PSPP, for statistical analysis of sampled data, by Ben Pfaff.

This file documents PSPP, a statistical package for analysis of sampled data that uses a command language compatible with SPSS.

Copyright (C) 1996-9, 2000 Free Software Foundation, Inc.

This version of the PSPP documentation is consistent with version 2 of ``texinfo.tex''.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above condition for modified versions, except that this permission notice may be stated in a translation approved by the Free Software Foundation.

PSPP
****

This file documents the PSPP package for statistical analysis of sampled data.  This is edition 0.2, for PSPP version 0.3, last modified at Time-stamp:  Sat Dec 20 20:25:33 WST 2003 jmd.

Introduction
************

PSPP is a tool for statistical analysis of sampled data.  It reads a syntax file and a data file, analyzes the data, and writes the results to a listing file or to standard output.

The language accepted by PSPP is similar to those accepted by SPSS statistical products.  The details of PSPP's language are given later in this manual.

PSPP produces output in two forms: tables and charts.  Both of these can be written in several formats; currently, ASCII, PostScript, and HTML are supported.  In the future, more drivers, such as PCL and X Window System drivers, may be developed.  For now, Ghostscript, available from the Free Software Foundation, may be used to convert PostScript chart output to other formats.

The current version of PSPP, 0.3, is woefully incomplete in terms of its statistical procedure support.  PSPP is a work in progress. The author hopes to support fully support all features in the products that PSPP replaces, eventually.  The author welcomes questions, comments, donations, and code submissions.  See Submitting Bug Reports, for instructions on contacting the author.

Your rights and obligations
***************************

Most of PSPP is distributed under the GNU General Public License.  The General Public License says, in effect, that you may modify and distribute PSPP as you like, as long as you grant the same rights to others.  It also states that you must provide source code when you distribute PSPP, or, if you obtained PSPP source code from an anonymous ftp site, give out the name of that site.

The General Public License is given in full in the source distribution as file COPYING.  In Debian GNU/Linux, this file is also available as file /usr/share/common-licenses/GPL-2.

To quote the GPL itself:

     This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

     This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more details.

     You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

Credits
*******

Most of PSPP, as well as this manual, was written by Ben Pfaff.  See Contacting the Author, for instructions on contacting the author.

The PSPP source code incorporates julcal10 originally written by Michael A. Covington and translated into C by Jim Van Zandt. The original package can be found in directory ftp://ftp.cdrom.com/pub/algorithms/c/julcal10.  The entire contents of that directory constitute the package.  The files actually used in PSPP are julcal.c and julcal.h.

Installing PSPP
***************

PSPP conforms to the GNU Coding Standards.  PSPP is written in, and requires for proper operation, ANSI/ISO C.  You might want to additionally note the following points:

  * The compiler and linker must allow for significance of several characters in external identifiers.  The exact number is unknown but at least 31 is recommended.

  * The int type must be 32 bits or wider.

  * The recommended compiler is gcc 2.7.2.1 or later, but any ANSI compiler will do if it fits the above criteria.

Many UNIX variants should work out-of-the-box, as PSPP uses GNU autoconf to detect differences between environments.  Please report any problems with compilation of PSPP under UNIX and UNIX-like operating systems---portability is a major concern of the author.

The pages below give specific instructions for installing PSPP on each type of system mentioned above.

UNIX installation
=================

To install PSPP under a UNIX-like operating system, follow the steps below in order.  Some of the text below was taken directly from various Free Software Foundation sources.

 1. cd to the directory containing the PSPP source.

 2. Type ./configure to configure for your particular operating system and compiler.  Running configure takes a while.  While running, it displays some messages telling which features it is checking for.

     You can optionally supply some options to configure to give it hints about how to do its job.  Type ./configure --help to see a list of options.  One of the most useful options is --with-checker, which enables the use of the Checker memory debugger under supported operating systems.  Checker must already be installed to use this option.  Do not use --with-checker if you are not debugging PSPP itself.

 3. (optional) Edit Makefile, config.h, and pref.h. These files are produced by configure.  Note that most PSPP settings can be changed at runtime.

     pref.h is only generated by configure if it does not already exist.  (It's copied from prefh.orig.)

 4. Type make to compile the package.  If there are any errors during compilation, try to fix them.  If modifications are necessary to compile correctly under your configuration, contact the author. See Submitting Bug Reports, for details.

 5. Type make check to run self-tests on the compiled PSPP package.

 6. Become the superuser and type make install to install the PSPP binaries, by default in /usr/local/bin/.  The directory /usr/local/share/pspp/ is created and populated with files needed by PSPP at runtime.  This step will also cause the PSPP documentation to be installed in /usr/local/info/, but only if that directory already exists.

 7. (optional) Type make clean to delete the PSPP binaries from the source tree.

Configuring PSPP
****************

PSPP has dozens of configuration possibilities and hundreds of settings.  This is both a bane and a blessing.  On one hand, it's possible to easily accommodate diverse ranges of setups.  But, on the other, the multitude of possibilities can overwhelm the casual user. Fortunately, the configuration mechanisms are profusely described in the sections below...

Locating configuration files
============================

PSPP uses the same method to find most of its configuration files:

 1. The base name of the file being sought is determined.

 2. The path to search is determined.

 3. Each directory in the search path, from left to right, is searched for a file with the name of the base name.  The first occurrence is read as the configuration file.

The first two steps are elaborated below for the sake of our pedantic friends.

 1. A base name is a file name lacking an absolute directory reference.  Some examples of base names are: ps-encodings, devices, devps/DESC (under UNIX), devps\DESC (under M$ environments).

     Determining the base name is a two-step process:

      a. If the appropriate environment variable is defined, the value of that variable is used (see Environment variables).  For instance, when searching for the output driver initialization file, the variable examined is STAT_OUTPUT_INIT_FILE.

      b. Otherwise, the compiled-in default is used.  For example, when searching for the output driver initialization file, the default base name is devices.

     Please note: If a user-specified base name does contain an absolute directory reference, as in a file name like /home/pfaff/fonts/TR, no path is searched---the file name is used exactly as given---and the algorithm terminates.

 2. The path is the first of the following that is defined:

       * A variable definition for the path given in the user environment.  This is a PSPP-specific environment variable name; for instance, STAT_OUTPUT_INIT_PATH.

       * In some cases, another, less-specific environment variable is checked. For instance, when searching for font files, the PostScript driver first checks for a variable with name STAT_GROFF_FONT_PATH, then for one with name GROFF_FONT_PATH.  (However, font searching has its own list of esoteric search rules.)

       * The configuration file path, which is itself determined by the following rules:

           a. If the command line contains an option of the form -B PATH or --config-dir=PATH, then the value given on the rightmost occurrence of such an option is used.

           b. Otherwise, if the environment variable STAT_CONFIG_PATH is defined, the value of that variable is used.

           c. Otherwise, the compiled-in fallback default is used.  On UNIX machines, the default fallback path is

                1. ~/.pspp

                2. /usr/local/lib/pspp

                3. /usr/lib/pspp

               On DOS machines, the default fallback path is:

                1. All the paths from the DOS search path in the PATH environment variable, in left-to-right order.

                2. C:\PSPP, as a last resort.

               Note that the installer of PSPP can easily change this default fallback path; thus the above should not be taken as gospel.

As a final note: Under DOS, directories given in paths are delimited by semicolons (;); under UNIX, directories are delimited by colons (:).  This corresponds with the standard path delimiter under these OSes.

Configuration techniques
========================

There are many ways that PSPP can be configured.  These are described in the list below.  Values given by earlier items take precedence over those given by later items.

 1. Syntax commands that modify settings, such as SET.  See SET.

 2. Command-line options.  See Invocation.

 3. PSPP-specific environment variable contents.  See Environment variables.

 4. General environment variable contents.  See Environment variables.

 5. Configuration file contents.  See Configuration files.

 6. Fallback defaults.

Some of the above may not apply to a particular setting.  For instance, the current pager (such as more, most, or less) cannot be determined by configuration file contents because there is no appropriate configuration file.

Configuration files
===================

Most configuration files have a common form:

  * Each line forms a separate command or directive.  This means that lines cannot be broken up, unless they are spliced together with a trailing backslash, as described below.

  * Before anything else is done, trailing whitespace is removed.

  * When a line ends in a backslash (\), the backslash is removed, and the next line is read and appended to the current line.

       - Whitespace preceding the backslash is retained.

       - This rule continues to be applied until the line read does not end in a backslash.

       - It is an error if the last line in the file ends in a backslash.

  * Comments are introduced by an octothorpe (#), and continue until the end of the line.

       - An octothorpe inside balanced pairs of double quotation marks (") or single quotation marks (') does not introduce a comment.

       - The backslash character can be used inside balanced quotes of either type to escape the following character as a literal character.

          (This is distinct from the use of a backslash as a line-splicing character.)

       - Line splicing takes place before comment removal.

  * Blank lines, and lines that contain only whitespace, are ignored.

Environment variables
=====================

You may think the concept of environment variables is a fairly simple one.  However, the author of PSPP has found a way to complicate even something so simple.  Environment variables are further described in the sections below:

Values of environment variables
-------------------------------

Values for environment variables are obtained by the following means, which are arranged in order of decreasing precedence:

 1. Command-line options.  See Invocation.

 2. The environment configuration file---more on this below.

 3. Actual environment variables (defined in the shell or other parent process).

The environment configuration file is located through application of the usual algorithm for configuration files (see File locations), except that its contents do not affect the search path used to find environment itself.  Use of environment is discouraged on systems that allow an arbitrarily large environment; it is supported for use on systems like MS-DOS that limit environment size.

environment is composed of lines having the form KEY=VALUE, where KEY and the equals sign (=) are required, and VALUE is optional.  If VALUE is given, variable KEY is given that value; if VALUE is absent, variable KEY is undefined (deleted).  Variables may not be defined with a null value.

Environment substitutions are performed on each line in the file (see Environment substitutions).

See Configuration files, for more details on formatting of the environment configuration file.

     Please note: Support for environment is not yet implemented.

Environment substitutions
-------------------------

Much of the power of environment variables lies in the way that they may be substituted into configuration files.  Variable substitutions are described below.

The line is scanned from left to right.  In this scan, all characters other than dollar signs ($) are retained unmolested.  Dollar signs, however, introduce an environment variable reference.  References take three forms:

$VAR
     Replaced by the value of environment variable VAR, determined as specified in Variable values.  VAR must be one of the following:

       * One or more letters.

       * Exactly one nonalphabetic character.  This may not be a left brace ({).

${VAR}
     Same as above, but VAR may contain any character (except }).

$$
     Replaced by a single dollar sign.

Undefined variables expand to a empty value.

Predefined environment variables
--------------------------------

There are two environment variables predefined for use in environment substitutions:

VER
     Defined as the version number of PSPP, as a string, in a format something like 0.9.4.

ARCH
     Defined as the host architecture of PSPP, as a string, in standard cpu-manufacturer-OS format.  For instance, Debian GNU/Linux 1.1 on an Intel machine defines this as i586-unknown-linux.  This is somewhat dependent on the system used to compile PSPP.

Nothing prevents these values from being overridden, although it's a good idea not to do so.

Output devices
==============

Configuring output devices is the most complicated aspect of configuring PSPP.  The output device configuration file is named devices.  It is searched for using the usual algorithm for finding configuration files (see File locations).  Each line in the file is read in the usual manner for configuration files (see Configuration files).

Lines in devices are divided into three categories, described briefly in the table below:

driver category definitions
     Define a driver in terms of other drivers.

macro definitions
     Define environment variables local to the the output driver configuration file.

device definitions
     Describe the configuration of an output device.

The following sections further elaborate the contents of the devices file.

Driver categories
-----------------

Drivers can be divided into categories.  Drivers are specified by their names, or by the names of the categories that they are contained in. Only certain drivers are enabled each time PSPP is run; by default, these are the drivers in the category `default'.  To enable a different set of drivers, use the -o DEVICE command-line option (see Invocation).

Categories are specified with a line of the form CATEGORY=DRIVER1 DRIVER2 DRIVER3 ... DRIVERN.  This line specifies that the category CATEGORY is composed of drivers named DRIVER1, DRIVER2, and so on.  There may be any number of drivers in the category, from zero on up.

Categories may also be specified on the command line (see Invocation).

This is all you need to know about categories.  If you're still curious, read on.

First of all, the term `categories' is a bit of a misnomer.  In fact, the internal representation is nothing like the hierarchy that the term seems to imply: a linear list is used to keep track of the enabled drivers.

When PSPP first begins reading devices, this list contains the name of any drivers or categories specified on the command line, or the single item `default' if none were specified.

Each time a category definition is specified, the list is searched for an item with the value of CATEGORY.  If a matching item is found, it is deleted.  If there was a match, the list of drivers (DRIVER1 through DRIVERN) is then appended to the list.

Each time a driver definition line is encountered, the list is searched. If the list contains an item with that driver's name, the driver is enabled and the item is deleted from the list.  Otherwise, the driver is not enabled.

It is an error if the list is not empty when the end of devices is reached.

Macro definitions
-----------------

Macro definitions take the form define MACRONAME DEFINITION.  In such a macro definition, the environment variable MACRONAME is defined to expand to the value DEFINITION. Before the definition is made, however, any macros used in DEFINITION are expanded.

Please note the following nuances of macro usage:

  * For the purposes of this section, macro and environment variable are synonyms.

  * Macros may not take arguments.

  * Macros may not recurse.

  * Macros are just environment variable definitions like other environment variable definitions, with the exception that they are limited in scope to the devices configuration file.

  * Macros override other all environment variables of the same name (within the scope of devices).

  * Earlier macro definitions for a particular KEY override later ones.  In particular, macro definitions on the command line override those in the device definition file.  See Non-option Arguments.

  * There are two predefined macros, whose values are determined at runtime:

     viewwidth
          Defined as the width of the console screen, in columns of text.

     viewlength
          Defined as the length of the console screen, in lines of text.

Driver definitions
------------------

Driver definitions are the ultimate purpose of the devices configuration file.  These are where the real action is.  Driver definitions tell PSPP where it should send its output.

Each driver definition line is divided into four fields.  These fields are delimited by colons (:).  Each line is subjected to environment variable interpolation before it is processed further (see Environment substitutions).  From left to right, the four fields are, in brief:

driver name
     A unique identifier, used to determine whether to enable the driver.

class name
     One of the predefined driver classes supported by PSPP.  The currently supported driver classes include `postscript' and `ascii'.

device type(s)
     Zero or more of the following keywords, delimited by spaces:

     screen

          Indicates that the device is a screen display.  This may reduce the amount of buffering done by the driver, to make interactive use more convenient.

     printer

          Indicates that the device is a printer.

     listing

          Indicates that the device is a listing file.

     These options are just hints to PSPP and do not cause the output to be directed to the screen, or to the printer, or to a listing file---those must be set elsewhere in the options.  They are used primarily to decide which devices should be enabled at any given time.  See SET, for more information.

options
     An optional set of options to pass to the driver itself.  The exact format for the options varies among drivers.

The driver is enabled if:

 1. Its driver name is specified on the command line, or

 2. It's in a category specified on the command line, or

 3. If no categories or driver names are specified on the command line, it is in category default.

For more information on driver names, see Driver categories.

The class name must be one of those supported by PSPP.  The classes supported depend on the options with which PSPP was compiled.  See later sections in this chapter for descriptions of the available driver classes.

Options are dependent on the driver.  See the driver descriptions for details.

Dimensions
----------

Quite often in configuration it is necessary to specify a length or a size.  PSPP uses a common syntax for all such, calling them collectively by the name dimensions.

  * You can specify dimensions in decimal form (12.5) or as fractions, either as mixed numbers (12-1/2) or raw fractions (25/2).

  * A number of different units are available.  These are suffixed to the numeric part of the dimension.  There must be no spaces between the number and the unit.  The available units are identical to those offered by the popular typesetting system TeX:

     in
          inch (1 in = 2.54 cm)

     "
          inch (1 in = 2.54 cm)

     pt
          printer's point (1 in = 72.27 pt)

     pc
          pica (12 pt = 1 pc)

     bp
          PostScript point (1 in = 72 bp)

     cm
          centimeter

     mm
          millimeter (10 mm = 1 cm)

     dd
          didot point (1157 dd = 1238 pt)

     cc
          cicero (1 cc = 12 dd)

     sp
          scaled point (65536 sp = 1 pt)

  * If no explicit unit is given, PSPP attempts to guess the best unit:

       - Numbers less than 50 are assumed to be in inches.

       - Numbers 50 or greater are assumed to be in millimeters.

Paper sizes
-----------

Output drivers usually deal with some sort of hardcopy media.  This media is called paper by the drivers, though in reality it could be a transparency or film or thinly veiled sarcasm.  To make it easier for you to deal with paper, PSPP allows you to have (of course!) a configuration file that gives symbolic names, like ``letter'' or ``legal'' or ``a4'', to paper sizes, rather than forcing you to use cryptic numbers like ``8-1/2 x 11'' or ``210 by 297''.  Surprisingly enough, this configuration file is named papersize. See Configuration files.

When PSPP tries to connect a symbolic paper name to a paper size, it reads and parses each non-comment line in the file, in order.  The first field on each line must be a symbolic paper name in double quotes. Paper names may not contain double quotes.  Paper names are not case-sensitive: legal and Legal are equivalent.

If a match is found for the paper name, the rest of the line is parsed. If it is found to be a pair of dimensions (see Dimensions) separated by either x or by, then those are taken to be the paper size, in order of width followed by length.  There must be at least one space on each side of x or by.

Otherwise the line must be of the form "PAPER-1"="PAPER-2".  In this case the target of the search becomes paper name PAPER-2 and the search through the file continues.

How lines are divided into types
--------------------------------

The lines in devices are distinguished in the following manner:

 1. Leading whitespace is removed.

 2. If the resulting line begins with the exact string define, followed by one or more whitespace characters, the line is processed as a macro definition.

 3. Otherwise, the line is scanned for the first instance of a colon (:) or an equals sign (=).

 4. If a colon is encountered first, the line is processed as a driver definition.

 5. Otherwise, if an equals sign is encountered, the line is processed as a macro definition.

 6. Otherwise, the line is ill-formed.

How lines are divided into tokens
---------------------------------

Each driver definition line is run through a simple tokenizer.  This tokenizer recognizes two basic types of tokens.

The first type is an equals sign (=).  Equals signs are both delimiters between tokens and tokens in themselves.

The second type is an identifier or string token.  Identifiers and strings are equivalent after tokenization, though they are written differently.  An identifier is any string of characters other than whitespace or equals sign.

A string is introduced by a single- or double-quote character (' or ") and, in general, continues until the next occurrence of that same character.  The following standard C escapes can also be embedded within strings:

\'
     A single-quote (').

\"
     A double-quote (").

\?
     A question mark (?).  Included for hysterical raisins.

\\
     A backslash (\).

\a
     Audio bell (ASCII 7).

\b
     Backspace (ASCII 8).

\f
     Formfeed (ASCII 12).

\n
     Newline (ASCII 10)

\r
     Carriage return (ASCII 13).

\t
     Tab (ASCII 9).

\v
     Vertical tab (ASCII 11).

\OOO
     Each o must be an octal digit.  The character is the one having the octal value specified.  Any number of octal digits is read and interpreted; only the lower 8 bits are used.

\xHH
     Each h must be a hex digit.  The character is the one having the hexadecimal value specified.  Any number of hex digits is read and interpreted; only the lower 8 bits are used.

Tokens, outside of quoted strings, are delimited by whitespace or equals signs.

The PostScript driver class
===========================

The postscript driver class is used to produce output that is acceptable to PostScript printers and to PC-based PostScript interpreters such as Ghostscript.  Continuing a long tradition, PSPP's PostScript driver is configurable to the point of absurdity.

There are actually two PostScript drivers.  The first one, postscript, produces ordinary DSC-compliant PostScript output. The second one epsf, produces an Encapsulated PostScript file. The two drivers are otherwise identical in configuration and in operation.

The PostScript driver is described in further detail below.

PostScript output options
-------------------------

These options deal with the form of the output and the output file itself:

output-file=FILENAME

     File to which output should be sent.  This can be an ordinary filename (i.e., "pspp.ps"), a pipe filename (i.e., "|lpr"), or stdout ("-").  Default: "pspp.ps".

color=BOOLEAN

     Most of the time black-and-white PostScript devices are smart enough to map colors to shades themselves.  However, you can cause the PSPP output driver to do an ugly simulation of this in its own driver by turning color off.  Default: on.

     This is a boolean setting, as are many settings in the PostScript driver.  Valid positive boolean values are on, true, yes, and nonzero integers.  Negative boolean values are off, false, no, and zero.

data=DATA-TYPE

     One of clean7bit, clean8bit, or binary.  This controls what characters will be written to the output file.  PostScript produced with clean7bit can be transmitted over 7-bit transmission channels that use ASCII control characters for line control.  clean8bit is similar but allows characters above 127 to be written to the output file.  binary allows any character in the output file.  Default: clean7bit.

line-ends=LINE-END-TYPE

     One of cr, lf, or crlf.  This controls what is used for newline in the output file.  Default: cr.

optimize-line-size=LEVEL

     Either 0 or 1.  If LEVEL is 1, then short line segments will be collected and merged into longer ones.  This reduces output file size but requires more time and memory.  A LEVEL of 0 has the advantage of being better for interactive environments.  1 is the default unless the screen flag is set; in that case, the default is 0.

optimize-text-size=LEVEL

     One of 0, 1, or 2, each higher level representing correspondingly more aggressive space savings for text in the output file and requiring correspondingly more time and memory.  Unfortunately the levels presently are all the same.  1 is the default unless the screen flag is set; in that case, the default is 0.

PostScript page options
-----------------------

These options affect page setup:

headers=BOOLEAN

     Controls whether the standard headers showing the time and date and title and subtitle are printed at the top of each page.  Default: on.

paper-size=PAPER-SIZE

     Paper size, either as a symbolic name (i.e., letter or a4) or specific measurements (i.e., 8-1/2x11 or "210 x 297". See Paper sizes.  Default: letter.

orientation=ORIENTATION

     Either portrait or landscape.  Default: portrait.

left-margin=DIMENSION
right-margin=DIMENSION
top-margin=DIMENSION
bottom-margin=DIMENSION

     Sets the margins around the page.  The headers, if enabled, are not included in the margins; they are in addition to the margins.  For a description of dimensions, see Dimensions.  Default: 0.5in.

PostScript file options
-----------------------

Oh, my.  You don't really want to know about the way that the PostScript driver deals with files, do you?  Well I suppose you're entitled, but I warn you right now: it's not pretty.  Here goes...

First let's look at the options that are available:

font-dir=FONT-DIRECTORY

     Sets the font directory.  Default: devps.

prologue-file=PROLOGUE-FILE-NAME

     Sets the name of the PostScript prologue file.  You can write your own prologue, though I have no idea why you'd want to: see Prologue. Default: ps-prologue.

device-file=DEVICE-FILE-NAME

     Sets the name of the Groff-format device description file.  The PostScript driver reads this to know about the scaling of fonts and so on.  The format of such files is described in groff_font(5), included with Groff.  Default: DESC.

encoding-file=ENCODING-FILE-NAME

     Sets the name of the encoding file.  This file contains a list of all font encodings that will be needed so that the driver can put all of them at the top of the prologue.  See Encodings.  Default: ps-encodings.

     If the specified encoding file cannot be found, this error will be silently ignored, since most people do not need any encodings besides the ones that can be found using auto-encodings, described below.

auto-encode=BOOLEAN

     When enabled, the font encodings needed by the default proportional- and fixed-pitch fonts will automatically be dumped to the PostScript output.  Otherwise, it is assumed that the user has an encoding file and knows how to use it (see Encodings).  There is probably no good reason to turn off this convenient feature.  Default: on.

Next I suppose it's time to describe the search algorithm.  When the PostScript driver needs a file, whether that file be a font, a PostScript prologue, or what you will, it searches in this manner:

 1. Constructs a path by taking the first of the following that is defined:

      a. Environment variable STAT_GROFF_FONT_PATH.  See Environment variables.

      b. Environment variable GROFF_FONT_PATH.

      c. The compiled-in fallback default.

 2. Constructs a base name from concatenating, in order, the font directory, a path separator (/ or \), and the file to be found.  A typical base name would be something like devps/ps-encodings.

 3. Searches for the base name in the path constructed above.  If the file is found, the algorithm terminates.

 4. Searches for the base name in the standard configuration path.  See File locations, for more details.  If the file is found, the algorithm terminates.

 5. At this point we remove the font directory and path separator from the base name.  Now the base name is simply the file to be found, i.e., ps-encodings.

 6. Searches for the base name in the path constructed in the first step. If the file is found, the algorithm terminates.

 7. Searches for the base name in the standard configuration path.  If the file is found, the algorithm terminates.

 8. The algorithm terminates unsuccessfully.

So, as you see, there are several ways to configure the PostScript drivers.  Careful selection of techniques can make the configuration very flexible indeed.

PostScript font options
-----------------------

The list of available font options is short and sweet:

prop-font=FONT-NAME

     Sets the default proportional font.  The name should be that of a PostScript font.  Default: "Helvetica".

fixed-font=FONT-NAME

     Sets the default fixed-pitch font.  The name should be that of a PostScript font.  Default: "Courier".

font-size=FONT-SIZE

     Sets the size of the default fonts, in thousandths of a point.  Default: 10000.

PostScript line options
-----------------------

Most tables contain lines, or rules, between cells.  Some features of the way that lines are drawn in PostScript tables are user-definable:

line-style=STYLE

     Sets the style used for lines used to divide tables into sections. STYLE must be either thick, in which case thick lines are used, or DOUBLE, in which case double lines are used.  Default: thick.

line-gutter=DIMENSION

     Sets the line gutter, which is the amount of whitespace on either side of lines that border text or graphics objects.  See Dimensions. Default: 0.5pt.

line-spacing=DIMENSION

     Sets the line spacing, which is the amount of whitespace that separates lines that are side by side, as in a double line.  Default: 0.5pt.

line-width=DIMENSION

     Sets the width of a typical line used in tables.  Default: 0.5pt.

line-width-thick=DIMENSION

     Sets the width of a thick line used in tables.  Not used if line-style is set to thick.  Default: 1.5pt.

The PostScript prologue
-----------------------

Most PostScript files that are generated mechanically by programs consist of two parts: a prologue and a body.  The prologue is generally a collection of boilerplate.  Only the body differs greatly between two outputs from the same program.

This is also the strategy used in the PSPP PostScript driver.  In general, the prologue supplied with PSPP will be more than sufficient. In this case, you will not need to read the rest of this section. However, hackers might want to know more.  Read on, if you fall into this category.

The prologue is dumped into the output stream essentially unmodified. However, two actions are performed on its lines.  First, certain lines may be omitted as specified in the prologue file itself.  Second, variables are substituted.

The following lines are omitted:

 1. All lines that contain three bangs in a row (!!!).

 2. Lines that contain !eps, if the PostScript driver is producing ordinary PostScript output.  Otherwise an EPS file is being produced, and the line is included in the output, although everything following !eps is deleted.

 3. Lines that contain !ps, if the PostScript driver is producing EPS output.  Otherwise, ordinary PostScript is being produced, and the line is included in the output, although everything following !ps is deleted.

The following are the variables that are substituted.  Only the variables listed are substituted; environment variables are not. See Environment substitutions.

bounding-box

     The page bounding box, in points, as four space-separated numbers.  For U.S. letter size paper, this is 0 0 612 792.

creator

     PSPP version as a string: GNU PSPP 0.1b, for example.

date

     Date the file was created.  Example: Tue May 21 13:46:22 1991.

data

     Value of the data PostScript driver option, as one of the strings Clean7Bit, Clean8Bit, or Binary.

orientation

     Page orientation, as one of the strings Portrait or Landscape.

user

     Under multiuser OSes, the user's login name, taken either from the environment variable LOGNAME or, if that fails, the result of the C library function getlogin().  Defaults to nobody.

host

     System hostname as reported by gethostname().  Defaults to nowhere.

prop-font

     Name of the default proportional font, prefixed by the word font and a space.  Example: font Times-Roman.

fixed-font

     Name of the default fixed-pitch font, prefixed by the word font and a space.

scale-factor

     The page scaling factor as a floating-point number.  Example: 1.0.  Note that this is also passed as an argument to the BP macro.

paper-length

paper-width

     The paper length and paper width, respectively, in thousandths of a point.  Note that these are also passed as arguments to the BP macro.

left-margin

top-margin

     The left margin and top margin, respectively, in thousandths of a point.  Note that these are also passed as arguments to the BP macro.

title

     Document title as a string.  This is not the title specified in the PSPP syntax file.  A typical title is the word PSPP followed by the syntax file name in parentheses.  Example: PSPP (<stdin>).

source-file

     PSPP syntax file name.  Example: mary96/first.stat.

Any other questions about the PostScript prologue can best be answered by examining the default prologue or the PSPP source.

PostScript encodings
--------------------

PostScript fonts often contain many more than 256 characters, in order to accommodate foreign language characters and special symbols. PostScript uses encodings to map these onto single-byte symbol sets.  Each font can have many different encodings applied to it.

PSPP's PostScript driver needs to know which encoding to apply to each font.  It can determine this from the information encapsulated in the Groff font description that it reads.  However, there is an additional problem---for efficiency, the PostScript driver needs to have a complete list of all encodings that will be used in the entire session when it opens the output file.  For this reason, it can't use the information built into the fonts because it doesn't know which fonts will be used.

As a stopgap solution, there are two mechanisms for specifying which encodings will be used.  The first mechanism is automatic and it is the only one that most PSPP users will ever need.  The second mechanism is manual, but it is more flexible.  Either mechanism or both may be used at one time.

The first mechanism is activated by the auto-encode driver option (see PS file options).  When enabled, auto-encode causes the PostScript driver to include the encodings used by the default proportional and fixed-pitch fonts (see PS font options).  Many PSPP output files will only need these encodings.

The second mechanism is the file specified by the encoding-file option (see PS file options).  If it exists, this file must consist of lines in PSPP configuration-file format (see Configuration files).  Each line that is not a comment should name a PostScript encoding to include in the output.

It is not an error if an encoding is included more than once, by either mechanism.  It will appear only once in the output.  It is also not an error if an encoding is included in the output but never used.  It is an error if an encoding is used but not included by one of these mechanisms.  In this case, the built-in PostScript encoding ISOLatin1Encoding is substituted.

The ASCII driver class
======================

The ASCII driver class produces output that can be displayed on a terminal or output to printers.  All of its options are highly configurable.  The ASCII driver has class name ascii.

The ASCII driver is described in further detail below.

ASCII output options
--------------------

output-file=FILENAME

     File to which output should be sent.  This can be an ordinary filename (e.g., "pspp.txt"), a pipe filename (e.g., "|lpr"), or stdout ("-").  Default: "pspp.list".

char-set=CHAR-SET-TYPE

     One of ascii or latin1.  This has no effect on output at the present time.  Default: ascii.

form-feed-string=FORM-FEED-VALUE

     The string written to the output to cause a formfeed.  See also paginate, described below, for a related setting.  Default: "\f".

newline-string=NEWLINE-VALUE

     The string written to the output to cause a newline (carriage return plus linefeed).  The default, which can be specified explicitly with newline-string=default, is to use the system-dependent newline sequence by opening the output file in text mode.  This is usually the right choice.

     However, newline-string can be set to any string.  When this is done, the output file is opened in binary mode.

paginate=BOOLEAN

     If set, a formfeed (as set in form-feed-string, described above) will be written to the device after every page.  Default: on.

tab-width=TAB-WIDTH-VALUE

     The distance between tab stops for this device.  If set to 0, tabs will not be used in the output.  Default: 8.

init=INITIALIZATION-STRING.

     String written to the device before anything else, at the beginning of the output.  Default: "" (the empty string).

done=FINALIZATION-STRING.

     String written to the device after everything else, at the end of the output.  Default: "" (the empty string).

ASCII page options
------------------

These options affect page setup:

headers=BOOLEAN

     If enabled, two lines of header information giving title and subtitle, page number, date and time, and PSPP version are printed at the top of every page.  These two lines are in addition to any top margin requested.  Default: on.

length=LINE-COUNT

     Physical length of a page, in lines.  Headers and margins are subtracted from this value.  Default: 66.

width=CHARACTER-COUNT

     Physical width of a page, in characters.  Margins are subtracted from this value.  Default: 130.

lpi=LINES-PER-INCH

     Number of lines per vertical inch.  Not currently used.  Default: 6.

cpi=CHARACTERS-PER-INCH

     Number of characters per horizontal inch.  Not currently used.  Default: 10.

left-margin=LEFT-MARGIN-WIDTH

     Width of the left margin, in characters.  PSPP subtracts this value from the page width.  Default: 0.

right-margin=RIGHT-MARGIN-WIDTH

     Width of the right margin, in characters.  PSPP subtracts this value from the page width.  Default: 0.

top-margin=TOP-MARGIN-LINES

     Length of the top margin, in lines.  PSPP subtracts this value from the page length.  Default: 2.

bottom-margin=BOTTOM-MARGIN-LINES

     Length of the bottom margin, in lines.  PSPP subtracts this value from the page length.  Default: 2.

ASCII font options
------------------

These are the ASCII font options:

box[LINE-TYPE]=BOX-CHARS

     The characters used for lines in tables produced by the ASCII driver can be changed using this option.  LINE-TYPE is used to indicate which type of line to change; BOX-CHARS is the character or string of characters to use for this type of line.

     LINE-TYPE must be a 4-digit number in base 4.  The digits are in the order `right', `bottom', `left', `top'.  The four possibilities for each digit are:

     0
          No line.

     1
          Single line.

     2
          Double line.

     3
          Special device-defined line, if one is available; otherwise, a double line.

     Examples:

     box[0101]="|"

          Sets | as the character to use for a single-width line with bottom and top components.

     box[2222]="#"

          Sets # as the character to use for the intersection of four double-width lines, one each from the top, bottom, left and right.

     box[1100]="\xda"

          Sets "\xda", which under MS-DOS is a box character suitable for the top-left corner of a box, as the character for the intersection of two single-width lines, one each from the right and bottom.

     Defaults:

       * box[0000]=" "

       * box[1000]="-"

          box[0010]="-"

          box[1010]="-"

       * box[0100]="|"

          box[0001]="|"

          box[0101]="|"

       * box[2000]="="

          box[0020]="="

          box[2020]="="

       * box[0200]="#"

          box[0002]="#"

          box[0202]="#"

       * box[3000]="="

          box[0030]="="

          box[3030]="="

       * box[0300]="#"

          box[0003]="#"

          box[0303]="#"

       * For all others, + is used unless there are double lines or special lines, in which case # is used.

italic-on=ITALIC-ON-STRING

     Character sequence written to turn on italics or underline printing.  If this is set to overstrike, then the driver will simulate underlining by overstriking with underscore characters (_) in the manner described by overstrike-style and carriage-return-style.  Default: overstrike.

italic-off=ITALIC-OFF-STRING

     Character sequence to turn off italics or underline printing.  Default: "" (the empty string).

bold-on=BOLD-ON-STRING

     Character sequence written to turn on bold or emphasized printing.  If set to overstrike, then the driver will simulated bold printing by overstriking characters in the manner described by overstrike-style and carriage-return-style.  Default: overstrike.

bold-off=BOLD-OFF-STRING

     Character sequence to turn off bold or emphasized printing.  Default: "" (the empty string).

bold-italic-on=BOLD-ITALIC-ON-STRING

     Character sequence written to turn on bold-italic printing.  If set to overstrike, then the driver will simulate bold-italics by overstriking twice, once with the character, a second time with an underscore (_) character, in the manner described by overstrike-style and carriage-return-style.  Default: overstrike.

bold-italic-off=BOLD-ITALIC-OFF-STRING

     Character sequence to turn off bold-italic printing.  Default: "" (the empty string).

overstrike-style=OVERSTRIKE-OPTION

     Either single or line:

       * If single is selected, then, to overstrike a line of text, the output driver will output a character, backspace, overstrike, output a character, backspace, overstrike, and so on along a line.

       * If line is selected then the output driver will output an entire line, then backspace or emit a carriage return (as indicated by carriage-return-style), then overstrike the entire line at once.

     single is recommended for use with ttys and programs that understand overstriking in text files, such as the pager less. single will also work with printer devices but results in rapid back-and-forth motions of the printhead that can cause the printer to physically overheat!

     line is recommended for use with printer devices.  Most programs that understand overstriking in text files will not properly deal with line mode.

     Default: single.

carriage-return-style=CARRIAGE-RETURN-TYPE

     Either bs or cr.  This option applies only when one or more of the font commands is set to overstrike and, at the same time, overstrike-style is set to line.

       * If bs is selected then the driver will return to the beginning of a line by emitting a sequence of backspace characters (ASCII 8).

       * If cr is selected then the driver will return to the beginning of a line by emitting a single carriage-return character (ASCII 13).

     Although cr is preferred as being more compact, bs is more general since some devices do not interpret carriage returns in the desired manner.  Default: bs.

The HTML driver class
=====================

The html driver class is used to produce output for viewing in tables-capable web browsers such as Emacs' w3-mode.  Its configuration is very simple.  Currently, the output has a very plain format.  In the future, further work may be done on improving the output appearance.

There are few options for use with the html driver class:

output-file=FILENAME

     File to which output should be sent.  This can be an ordinary filename (i.e., "pspp.ps"), a pipe filename (i.e., "|lpr"), or stdout ("-").  Default: "pspp.html".

prologue-file=PROLOGUE-FILE-NAME

     Sets the name of the PostScript prologue file.  You can write your own prologue if you want to customize colors or other settings: see HTML Prologue.  Default: html-prologue.

The HTML prologue
-----------------

HTML files that are generated by PSPP consist of two parts: a prologue and a body.  The prologue is a collection of boilerplate.  Only the body differs greatly between two outputs.  You can tune the colors and other attributes of the output by editing the prologue.

The prologue is dumped into the output stream essentially unmodified. However, two actions are performed on its lines.  First, certain lines may be omitted as specified in the prologue file itself.  Second, variables are substituted.

The following lines are omitted:

 1. All lines that contain three bangs in a row (!!!).

 2. Lines that contain !title, if no title is set for the output.  If a title is set, then the characters !title are removed before the line is output.

 3. Lines that contain !subtitle, if no subtitle is set for the output.  If a subtitle is set, then the characters !subtitle are removed before the line is output.

The following are the variables that are substituted.  Only the variables listed are substituted; environment variables are not. See Environment substitutions.

generator

     PSPP version as a string: GNU PSPP 0.1b, for example.

date

     Date the file was created.  Example: Tue May 21 13:46:22 1991.

user

     Under multiuser OSes, the user's login name, taken either from the environment variable LOGNAME or, if that fails, the result of the C library function getlogin().  Defaults to nobody.

host

     System hostname as reported by gethostname().  Defaults to nowhere.

title

     Document title as a string.  This is the title specified in the PSPP syntax file.

subtitle

     Document subtitle as a string.

source-file

     PSPP syntax file name.  Example: mary96/first.stat.

Miscellaneous configuration
===========================

The following environment variables can be used to further configure PSPP:

HOME

     Used to determine the user's home directory.  No default value.

STAT_INCLUDE_PATH

     Path used to find include files in PSPP syntax files.  Defaults vary across operating systems:

     UNIX

            * .

            * ~/.pspp/include

            * /usr/local/lib/pspp/include

            * /usr/lib/pspp/include

            * /usr/local/share/pspp/include

            * /usr/share/pspp/include

     MS-DOS

            * .

            * C:\PSPP\INCLUDE

            * $PATH

     Other OSes
          No default path.

STAT_PAGER
PAGER

     When PSPP invokes an external pager, it uses the first of these that is defined.  There is a default pager only if the person who compiled PSPP defined one.

TERM

     The terminal type termcap or ncurses will use, if such support was compiled into PSPP.

STAT_OUTPUT_INIT_FILE

     The basename used to search for the driver definition file. See Output devices.  See File locations.  Default: devices.

STAT_OUTPUT_PAPERSIZE_FILE

     The basename used to search for the papersize file.  See papersize. See File locations.  Default: papersize.

STAT_OUTPUT_INIT_PATH

     The path used to search for the driver definition file and the papersize file.  See File locations.  Default: the standard configuration path.

TMPDIR

     The sort procedure stores its temporary files in this directory. Default: (UNIX) /tmp, (MS-DOS) \, (other OSes) empty string.

TEMP

TMP

     Under MS-DOS only, these variables are consulted after TMPDIR, in this order.

Improving output quality
========================

When its drivers are set up properly, PSPP can produce output that looks very good indeed.  The PostScript driver, suitably configured, can produce presentation-quality output.  Here are a few guidelines for producing better-looking output, regardless of output driver.  Your mileage may vary, of course, and everyone has different esthetic preferences.

  * Width is important in PSPP output.  Greater output width leads to more readable output, to a point.  Try the following to increase the output width:

       - If you're using the ASCII driver with a dot-matrix printer, figure out what you need to do to put the printer into compressed mode.  Put that string into the init-string setting.  Try to get 132 columns; 160 might be better, but you might find that print that tiny is difficult to read.

       - With the PostScript driver, try these ideas:

            + Landscape mode.

            + Legal-size (8.5" x 14") paper in landscape mode.

            + Reducing font sizes.  If you're using 12-point fonts, try 10 point; if you're using 10-point fonts, try 8 point.  Some fonts are more readable than others at small sizes.

     Try to strike a balance between character size and page width.

  * Use high-quality fonts.  Many public domain fonts are poor in quality. Recently, URW made some high-quality fonts available under the GPL. These are probably suitable.

  * Be sure you're using the proper font metrics.  The font metrics provided with PSPP may not correspond to the fonts actually being printed. This can cause bizarre-looking output.

  * Make sure that you're using good ink/ribbon/toner.  Darker print is easier to read.

  * Use plain fonts with serifs, such as Times-Roman or Palatino.  Avoid choosing italic or bold fonts as document base fonts.

Invoking PSPP
*************

     pspp [ -B DIR | --config-dir=DIR ] [ -o DEVICE | --device=DEVICE ]
            [ -d VAR[=VALUE] | --define=VAR[=VALUE] ] [-u VAR | --undef=VAR ]
            [ -f FILE | --out-file=FILE ] [ -p | --pipe ] [ -I- | --no-include ]
            [ -I DIR | --include=DIR ] [ -i | --interactive ]
            [ -n | --edit | --dry-run | --just-print | --recon ]
            [ -r | --no-statrc ] [ -h | --help ] [ -l | --list ]
            [ -c COMMAND | --command COMMAND ] [ -s | --safer ]
            [ --testing-mode ] [ -V | --version ] [ -v | --verbose ]
            [ KEY=VALUE ] FILE...

Non-option Arguments
====================

Syntax files and output device substitutions can be specified on PSPP's command line:

FILE

     A file by itself on the command line will be executed as a syntax file. PSPP terminates after the syntax file runs, unless the -i or --interactive option is given (see Language control options).

FILE1 FILE2

     When two or more filenames are given on the command line, the first syntax file is executed, then PSPP's dictionary is cleared, then the second syntax file is executed.

FILE1 + FILE2

     If syntax files' names are delimited by a plus sign (+), then the dictionary is not cleared between their executions, as if they were concatenated together into a single file.

KEY=VALUE

     Defines an output device macro KEY to expand to VALUE, overriding any macro having the same KEY defined in the device configuration file.  See Macro definitions.

There is one other way to specify a syntax file, if your operating system supports it.  If you have a syntax file foobar.stat, put the notation

     #! /usr/local/bin/pspp

at the top, and mark the file as executable with chmod +x foobar.stat.  (If PSPP is not installed in /usr/local/bin, then insert its actual installation directory into the syntax file instead.)  Now you should be able to invoke the syntax file just by typing its name.  You can include any options on the command line as usual.  PSPP entirely ignores any lines beginning with #!.

Configuration Options
=====================

Configuration options are used to change PSPP's configuration for the current run.  The configuration options are:

-B DIR
--config-dir=DIR

     Sets the configuration directory to DIR.  See File locations.

-o DEVICE
--device=DEVICE

     Selects the output device with name DEVICE.  If this option is given more than once, then all devices mentioned are selected.  This option disables all devices besides those mentioned on the command line.

-d VAR[=VALUE]
--define=VAR[=VALUE]

     Defines an `environment variable' named VAR having the optional value VALUE specified.  See Variable values.

-u VAR
--undef=VAR

     Undefines the `environment variable' named VAR.  See Variable values.

Input and output options
========================

Input and output options affect how PSPP reads input and writes output.  These are the input and output options:

-f FILE
--out-file=FILE

     This overrides the output file name for devices designated as listing devices.  If a file named FILE already exists, it is overwritten.

-p
--pipe

     Allows PSPP to be used as a filter by causing the syntax file to be read from stdin and output to be written to stdout.  Conflicts with the -f FILE and --file=FILE options.

-I-
--no-include

     Clears all directories from the include path.  This includes all directories put in the include path by default.  See Miscellaneous configuring.

-I DIR
--include=DIR

     Appends directory DIR to the path that is searched for include files in PSPP syntax files.

-c COMMAND
--command=COMMAND

     Execute literal command COMMAND.  The command is executed before startup syntax files, if any.

--testing-mode

     Invoke heuristics to assist with testing PSPP.  For use by make check and similar scripts.

Language control options
========================

Language control options control how PSPP syntax files are parsed and interpreted.  The available language control options are:

-i
--interactive

     When a syntax file is specified on the command line, PSPP normally terminates after processing it.  Giving this option will cause PSPP to bring up a command prompt after processing the syntax file.

     In addition, this forces syntax files to be interpreted in interactive mode, rather than the default batch mode.  See Tokenizing lines, for information on the differences between batch mode and interactive mode command interpretation.

-n
--edit
--dry-run
--just-print
--recon

     Only the syntax of any syntax file specified or of commands entered at the command line is checked.  Transformations are not performed and procedures are not executed.  Not yet implemented.

-r
--no-statrc

     Prevents the execution of the PSPP startup syntax file.  Not yet implemented, as startup syntax files aren't, either.

-s
--safer

     Disables certain unsafe operations.  This includes the ERASE and HOST commands, as well as use of pipes as input and output files.

Informational options
=====================

Informational options cause information about PSPP to be written to the terminal.  Here are the available options:

-h

--help

     Prints a message describing PSPP command-line syntax and the available device driver classes, then terminates.

-l

--list

     Lists the available device driver classes, then terminates.

-V

--version

     Prints a brief message listing PSPP's version, warranties you don't have, copying conditions and copyright, and e-mail address for bug reports, then terminates.

-v

--verbose

     Increments PSPP's verbosity level.  Higher verbosity levels cause PSPP to display greater amounts of information about what it is doing.  Often useful for debugging PSPP's configuration.

     This option can be given multiple times to set the verbosity level to that value.  The default verbosity level is 0, in which no informational messages will be displayed.

     Higher verbosity levels cause messages to be displayed when the corresponding events take place.

     1

          Driver and subsystem initializations.

     2

          Completion of driver initializations.  Beginning of driver closings.

     3

          Completion of driver closings.

     4

          Files searched for; success of searches.

     5

          Individual directories included in file searches.

     Each verbosity level also includes messages from lower verbosity levels.

The PSPP language
*****************

     Please note: PSPP is not even close to completion. Only a few actual statistical procedures are implemented.  PSPP is a work in progress.

This chapter discusses elements common to many PSPP commands. Later chapters will describe individual commands in detail.

Tokens
======

PSPP divides most syntax file lines into series of short chunks called tokens, lexical elements, or lexemes.  These tokens are then grouped to form commands, each of which tells PSPP to take some action---read in data, write out data, perform a statistical procedure, etc.  The process of dividing input into tokens is tokenization, or lexical analysis.  Each type of token is described below.

Tokens must be separated from each other by delimiters. Delimiters include whitespace (spaces, tabs, carriage returns, line feeds, vertical tabs), punctuation (commas, forward slashes, etc.), and operators (plus, minus, times, divide, etc.)  Note that while whitespace only separates tokens, other delimiters are tokens in themselves.

Identifiers
     Identifiers are names that specify variable names, commands, or command details.

       * The first character in an identifier must be a letter, #, or @.  Some system identifiers begin with $, but user-defined variables' names may not begin with $.

       * The remaining characters in the identifier must be letters, digits, or one of the following special characters:

               .  _  $  #  @

       * Variable names may be any length, but only the first 8 characters are significant.

       * Identifiers are not case-sensitive: foobar, Foobar, FooBar, FOOBAR, and FoObaR are different representations of the same identifier.

       * Identifiers other than variable names may be abbreviated to their first 3 characters if this abbreviation is unambiguous.  These identifiers are often called keywords.  (Unique abbreviations of 3 or more characters are also accepted: FRE, FREQ, and FREQUENCIES are equivalent when the last is a keyword.)

       * Whether an identifier is a keyword depends on the context.

       * Some keywords are reserved.  These keywords may not be used in any context besides those explicitly described in this manual.  The reserved keywords are:

               ALL  AND  BY  EQ  GE  GT  LE  LT  NE  NOT  OR  TO  WITH

       * Since keywords are identifiers, all the rules for identifiers apply. Specifically, they must be delimited as are other identifiers: WITH is a reserved keyword, but WITHOUT is a valid variable name.

     Caution: It is legal to end a variable name with a period, but don't do it!  The variable name will be misinterpreted when it is the final token on a line: FOO. will be divided into two separate tokens, FOO and ., the terminal dot. See Forming commands of tokens.

Numbers
     Numbers may be specified as integers or reals.  Integers are internally converted into reals.  Scientific notation is not supported.  Here are some examples of valid numbers:

          1234  3.14159265359  .707106781185  8945.

     Caution: The last example will be interpreted as two tokens, 8945 and ., if it is the last token on a line.

Strings
     Strings are literal sequences of characters enclosed in pairs of single quotes (') or double quotes (").

       * Whitespace and case of letters are significant inside strings.

       * Whitespace characters inside a string are not delimiters.

       * To include single-quote characters in a string, enclose the string in double quotes.

       * To include double-quote characters in a string, enclose the string in single quotes.

       * It is not possible to put both single- and double-quote characters inside one string.

Hexstrings
     Hexstrings are string variants that use hex digits to specify characters.

       * A hexstring may be used anywhere that an ordinary string is allowed.

       * A hexstring begins with X' or x', and ends with '.

       * No whitespace is allowed between the initial X and '.

       * Double quotes " may be used in place of single quotes ' if done in both places.

       * Each pair of hex digits is internally changed into a single character with the given value.

       * If there is an odd number of hex digits, the missing last digit is assumed to be 0.

       * Please note: Use of hexstrings is nonportable because the same numeric values are associated with different glyphs by different operating systems.  Therefore, their use should be confined to syntax files that will not be widely distributed.

       * Please note also: The character with value 00 is reserved for internal use by PSPP.  Its use in strings causes an error and replacement with a blank space (in ASCII, hex 20, decimal 32).

Punctuation
     Punctuation separates tokens; punctuators are delimiters.  These are the punctuation characters:

          ,  /  =  (  )

Operators
     Operators describe mathematical operations.  Some operators are delimiters:

          (  )  +  -  *  /  **

     Many of the above operators are also punctuators.  Punctuators are distinguished from operators by context.

     The other operators are all reserved keywords.  None of these are delimiters:

          AND  EQ  GE  GT  LE  LT  NE  OR

Terminal Dot
     A period (.) at the end of a line (except for whitespace) is one type of a terminal dot, although not every terminal dot is a period at the end of a line.  See Forming commands of tokens.  A period is a terminal dot only when it is at the end of a line; otherwise it is part of a floating-point number.  (A period outside a number in the middle of a line is an error.)

          Please note: The character used for the terminal dot can be changed with SET's ENDCMD subcommand (see SET).  This is strongly discouraged, and throughout all the remainder of this manual it will be assumed that the default setting is in effect.

Forming commands of tokens
==========================

Most PSPP commands share a common structure, diagrammed below:

     CMD... [SBC[=][SPEC [[,]SPEC]...]] [[/[=][SPEC [[,]SPEC]...]]...].

In the above, rather daunting, expression, pairs of square brackets ([ ]) indicate optional elements, and names such as CMD indicate parts of the syntax that vary from command to command. Ellipses (...) indicate that the preceding part may be repeated an arbitrary number of times.  Let's pick apart what it says above:

  * A command begins with a command name of one or more keywords, such as FREQUENCIES, DATA LIST, or N OF CASES.  CMD may be abbreviated to its first word if that is unambiguous; each word in CMD may be abbreviated to a unique prefix of three or more characters as described above.

  * The command name may be followed by one or more subcommands:

       - Each subcommand begins with a unique keyword, indicated by SBC above.  This is analogous to the command name.

       - The subcommand name is optionally followed by an equals sign (=).

       - Some subcommands accept a series of one or more specifications (SPEC), optionally separated by commas.

       - Each subcommand must be separated from the next (if any) by a forward slash (/).

  * Each command must be terminated with a terminal dot. The terminal dot may be given one of three ways:

       - (most commonly) A period character at the very end of a line, as described above.

       - (only if NULLINE is on: see Setting user preferences, for more details.)  A completely blank line.

       - (in batch mode only) Any line that is not indented from the left side of the page causes a terminal dot to be inserted before that line. Therefore, each command begins with a line that is flush left, followed by zero or more lines that are indented one or more characters from the left margin.

          In batch mode, PSPP will ignore a plus sign, minus sign, or period (+, -, or .) as the first character in a line.  Any of these characters as the first character on a line will begin a new command.  This allows for visual indentation of a command without that command being considered part of the previous command.

          PSPP is in batch mode when it is reading input from a file, rather than from an interactive user.  Note that the other forms of the terminal dot may also be used in batch mode.

          Sometimes, one encounters syntax files that are intended to be interpreted in interactive mode rather than batch mode (for instance, this can happen if a session log file is used directly as a syntax file).  When this occurs, use the -i command line option to force interpretation in interactive mode (see Language control options).

PSPP ignores empty commands when they are generated by the above rules.  Note that, as a consequence of these rules, each command must begin on a new line.

Types of Commands
=================

Commands in PSPP are divided roughly into six categories:

Utility commands
     Set or display various global options that affect PSPP operations. May appear anywhere in a syntax file.  See Utility commands.

File definition commands
     Give instructions for reading data from text files or from special binary ``system files''.  Most of these commands discard any previous data or variables to replace it with the new data and variables.  At least one must appear before the first command in any of the categories below.  See Data Input and Output.

Input program commands
     Though rarely used, these provide powerful tools for reading data files in arbitrary textual or binary formats.  See INPUT PROGRAM.

Transformations
     Perform operations on data and write data to output files.  Transformations are not carried out until a procedure is executed.

Restricted transformations
     Same as transformations for most purposes.  See Order of Commands, for a detailed description of the differences.

Procedures
     Analyze data, writing results of analyses to the listing file.  Cause transformations specified earlier in the file to be performed.  In a more general sense, a procedure is any command that causes the active file (the data) to be read.

Order of Commands
=================

PSPP does not place many restrictions on ordering of commands. The main restriction is that variables must be defined with one of the file-definition commands before they are otherwise referred to.

Of course, there are specific rules, for those who are interested. PSPP possesses five internal states, called initial, INPUT PROGRAM, FILE TYPE, transformation, and procedure states.  (Please note the distinction between the INPUT PROGRAM and FILE TYPE commands and the INPUT PROGRAM and FILE TYPE states.)

PSPP starts up in the initial state.  Each successful completion of a command may cause a state transition.  Each type of command has its own rules for state transitions:

Utility commands

       * Legal in all states.

       * Do not cause state transitions.  Exception: when N OF CASES is executed in the procedure state, it causes a transition to the transformation state.

DATA LIST

       * Legal in all states.

       * When executed in the initial or procedure state, causes a transition to the transformation state.

       * Clears the active file if executed in the procedure or transformation state.

INPUT PROGRAM

       * Invalid in INPUT PROGRAM and FILE TYPE states.

       * Causes a transition to the INPUT PROGRAM state.

       * Clears the active file.

FILE TYPE

       * Invalid in INPUT PROGRAM and FILE TYPE states.

       * Causes a transition to the FILE TYPE state.

       * Clears the active file.

Other file definition commands

       * Invalid in INPUT PROGRAM and FILE TYPE states.

       * Cause a transition to the transformation state.

       * Clear the active file, except for ADD FILES, MATCH FILES, and UPDATE.

Transformations

       * Invalid in initial and FILE TYPE states.

       * Cause a transition to the transformation state.

Restricted transformations

       * Invalid in initial, INPUT PROGRAM, and FILE TYPE states.

       * Cause a transition to the transformation state.

Procedures

       * Invalid in initial, INPUT PROGRAM, and FILE TYPE states.

       * Cause a transition to the procedure state.

Handling missing observations
=============================

PSPP includes special support for unknown numeric data values. Missing observations are assigned a special value, called the system-missing value.  This ``value'' actually indicates the absence of value; it means that the actual value is unknown.  Procedures automatically exclude from analyses those observations or cases that have missing values.  Whether single observations or entire cases are excluded depends on the procedure.

The system-missing value exists only for numeric variables.  String variables always have a defined value, even if it is only a string of spaces.

Variables, whether numeric or string, can have designated user-missing values.  Every user-missing value is an actual value for that variable.  However, most of the time user-missing values are treated in the same way as the system-missing value.  String variables that are wider than a certain width, usually 8 characters (depending on computer architecture), cannot have user-missing values.

For more information on missing values, see the following sections: Variables, MISSING VALUES, Expressions.  See also the documentation on individual procedures for information on how they handle missing values.

Variables
=========

Variables are the basic unit of data storage in PSPP.  All the variables in a file taken together, apart from any associated data, are said to form a dictionary. Some details of variables are described in the sections below.

Attributes of Variables
-----------------------

Each variable has a number of attributes, including:

Name
     This is an identifier.  Each variable must have a different name. See Tokens.

Type
     Numeric or string.

Width
     (string variables only) String variables with a width of 8 characters or fewer are called short string variables.  Short string variables can be used in many procedures where long string variables (those with widths greater than 8) are not allowed.

          Please note: Certain systems may consider strings longer than 8 characters to be short strings.  Eight characters represents a minimum figure for the maximum length of a short string.

Position
     Variables in the dictionary are arranged in a specific order. DISPLAY can be used to show this order: see DISPLAY.

Initialization
     Either reinitialized to 0 or spaces for each case, or left at its existing value.  See LEAVE.

Missing values
     Optionally, up to three values, or a range of values, or a specific value plus a range, can be specified as user-missing values. There is also a system-missing value that is assigned to an observation when there is no other obvious value for that observation. Observations with missing values are automatically excluded from analyses.  User-missing values are actual data values, while the system-missing value is not a value at all.  See Missing Observations.

Variable label
     A string that describes the variable.  See VARIABLE LABELS.

Value label
     Optionally, these associate each possible value of the variable with a string.  See VALUE LABELS.

Print format
     Display width, format, and (for numeric variables) number of decimal places.  This attribute does not affect how data are stored, just how they are displayed.  Example: a width of 8, with 2 decimal places. See PRINT FORMATS.

Write format
     Similar to print format, but used by certain commands that are designed to write to binary files.  See WRITE FORMATS.

Variables Automatically Defined by PSPP
---------------------------------------

There are seven system variables.  These are not like ordinary variables, as they are not stored in each case.  They can only be used in expressions.  These system variables, whose values and output formats cannot be modified, are described below.

$CASENUM
     Case number of the case at the moment.  This changes as cases are shuffled around.

$DATE
     Date the PSPP process was started, in format A9, following the pattern DD MMM YY.

$JDATE
     Number of days between 15 Oct 1582 and the time the PSPP process was started.

$LENGTH
     Page length, in lines, in format F11.

$SYSMIS
     System missing value, in format F1.

$TIME
     Number of seconds between midnight 14 Oct 1582 and the time the active file was read, in format F20.

$WIDTH
     Page width, in characters, in format F3.

Lists of variable names
-----------------------

There are several ways to specify a set of variables:

 1. (Most commonly.)  List the variable names one after another, optionally separating them by commas.

 2. (This method cannot be used on commands that define the dictionary, such as DATA LIST.)  The syntax is the names of two existing variables, separated by the reserved keyword TO.  The meaning is to include every variable in the dictionary between and including the variables specified.  For instance, if the dictionary contains six variables with the names ID, X1, X2, GOAL, MET, and NEXTGOAL, in that order, then X2 TO MET would include variables X2, GOAL, and MET.

 3. (This method can be used only on commands that define the dictionary, such as DATA LIST.)  It is used to define sequences of variables that end in consecutive integers.  The syntax is two identifiers that end in numbers.  This method is best illustrated with examples:

       * The syntax X1 TO X5 defines 5 variables:

            - X1

            - X2

            - X3

            - X4

            - X5

       * The syntax ITEM0008 TO ITEM0013 defines 6 variables:

            - ITEM0008

            - ITEM0009

            - ITEM0010

            - ITEM0011

            - ITEM0012

            - ITEM0013

       * Each of the syntaxes QUES001 TO QUES9 and QUES6 TO QUES3 are invalid, although for different reasons, which should be evident.

     Note that after a set of variables has been defined with DATA LIST or another command with this method, the same set can be referenced on later commands using the same syntax.

 4. The above methods can be combined, either one after another or delimited by commas.  For instance, the combined syntax A Q5 TO Q8 X TO Z is legal as long as each part A, Q5 TO Q8, X TO Z is individually legal.

Input and Output Formats
------------------------

Data that PSPP inputs and outputs must have one of a number of formats. These formats are described, in general, by a format specification of the form NAMEw.d, where NAME is the format name and W is a field width.  D is the optional desired number of decimal places, if appropriate.  If D is not included then it is assumed to be 0.  Some formats do not allow D to be specified.

When an input format is specified on DATA LIST or another command, then it is converted to an output format for the purposes of PRINT and other data output commands.  For most purposes, input and output formats are the same; the salient differences are described below.

Below are listed the input and output formats supported by PSPP.  If an input format is mapped to a different output format by default, then that mapping is indicated with =>.  Each format has the listed bounds on input width (iw) and output width (ow).

The standard numeric input and output formats are given in the following table:

Fw.d: 1 <= iw,ow <= 40
     Standard decimal format with D decimal places.  If the number is too large to fit within the field width, it is expressed in scientific notation (1.2+34) if w >= 6, with always at least two digits in the exponent.  When used as an input format, scientific notation is allowed but an E or an F must be used to introduce the exponent.

     The default output format is the same as the input format, except if D > 1.  In that case the output W is always made to be at least 2 + D.

Ew.d: 1 <= iw <= 40; 6 <= ow <= 40
     For input this is equivalent to F format except that no E or F is require to introduce the exponent.  For output, produces scientific notation in the form 1.2+34.  There are always at least two digits given in the exponent.

     The default output W is the largest of the input W, the input D + 7, and 10.  The default output D is the input D, but at least 3.

COMMAw.d: 1 <= iw,ow <= 40
     Equivalent to F format, except that groups of three digits are comma-separated on output.  If the number is too large to express in the field width, then first commas are eliminated, then if there is still not enough space the number is expressed in scientific notation given that w >= 6.  Commas are allowed and ignored when this is used as an input format.

DOTw.d: 1 <= iw,ow <= 40
     Equivalent to COMMA format except that the roles of comma and decimal point are interchanged.  However: If SET /DECIMAL=DOT is in effect, then COMMA uses , for a decimal point and DOT uses . for a decimal point.

DOLLARw.d: 1 <= iw <= 40; 2 <= ow <= 40
     Equivalent to COMMA format, except that the number is prefixed by a dollar sign ($) if there is room.  On input the value is allowed to be prefixed by a dollar sign, which is ignored.

     The default output W is the input W, but at least 2.

PCTw.d: 2 <= iw,ow <= 40
     Equivalent to F format, except that the number is suffixed by a percent sign (%) if there is room.  On input the value is allowed to be suffixed by a percent sign, which is ignored.

     The default output W is the input W, but at least 2.

Nw.d: 1 <= iw,ow <= 40
     Only digits are allowed within the field width.  The decimal point is assumed to be D digits from the right margin.

     The default output format is F with the same W and D, except if D > 1.  In that case the output W is always made to be at least 2 + D.

Zw.d => F: 1 <= iw,ow <= 40
     Zoned decimal input.  If you need to use this then you know how.

IBw.d => F: 1 <= iw,ow <= 8
     Integer binary format.  The field is interpreted as a fixed-point positive or negative binary number in two's-complement notation.  The location of the decimal point is implied.  Endianness is the same as the host machine.

     The default output format is F8.2 if D is 0.  Otherwise it is F, with output W as 9 + input D and output D as input D.

PIB => F: 1 <= iw,ow <= 8
     Positive integer binary format.  The field is interpreted as a fixed-point positive binary number.  The location of the decimal point is implied.  Endianness is teh same as the host machine.

     The default output format follows the rules for IB format.

Pw.d => F: 1 <= iw,ow <= 16
     Binary coded decimal format.  Each byte from left to right, except the rightmost, represents two digits.  The upper nibble of each byte is more significant.  The upper nibble of the final byte is the least significant digit.  The lower nibble of the final byte is the sign; a value of D represents a negative sign and all other values are considered positive.  The decimal point is implied.

     The default output format follows the rules for IB format.

PKw.d => F: 1 <= iw,ow <= 16
     Positive binary code decimal format.  Same as P but the last byte is the same as the others.

     The default output format follows the rules for IB format.

RBw => F: 2 <= iw,ow <= 8

     Binary C architecture-dependent ``double'' format.  For a standard IEEE754 implementation W should be 8.

     The default output format follows the rules for IB format.

PIBHEXw.d => F: 2 <= iw,ow <= 16
     PIB format encoded as textual hex digit pairs.  W must be even.

     The input width is mapped to a default output width as follows: 2=>4, 4=>6, 6=>9, 8=>11, 10=>14, 12=>16, 14=>18, 16=>21.  No allowances are made for decimal places.

RBHEXw => F: 4 <= iw,ow <= 16

     RB format encoded as textual hex digits pairs.  W must be even.

     The default output format is F8.2.

CCAw.d: 1 <= ow <= 40
CCBw.d: 1 <= ow <= 40
CCCw.d: 1 <= ow <= 40
CCDw.d: 1 <= ow <= 40
CCEw.d: 1 <= ow <= 40

     User-defined custom currency formats.  May not be used as an input format.  See SET, for more details.

The date and time numeric input and output formats accept a number of possible formats.  Before describing the formats themselves, some definitions of the elements that make up their formats will be helpful:

leader
     All formats accept an optional whitespace leader.

day
     An integer between 1 and 31 representing the day of month.

day-count
     An integer representing a number of days.

date-delimiter
     One or more characters of whitespace or the following characters: - / . ,

month
     A month name in one of the following forms:

       * An integer between 1 and 12.

       * Roman numerals representing an integer between 1 and 12.

       * At least the first three characters of an English month name (January, February, ...).

year
     An integer year number between 1582 and 19999, or between 1 and 199. Years between 1 and 199 will have 1900 added.

julian
     A single number with a year number in the first 2, 3, or 4 digits (as above) and the day number within the year in the last 3 digits.

quarter
     An integer between 1 and 4 representing a quarter.

q-delimiter
     The letter Q or q.

week
     An integer between 1 and 53 representing a week within a year.

wk-delimiter
     The letters wk in any case.

time-delimiter
     At least one characters of whitespace or : or ..

hour
     An integer greater than 0 representing an hour.

minute
     An integer between 0 and 59 representing a minute within an hour.

opt-second
     Optionally, a time-delimiter followed by a real number representing a number of seconds.

hour24
     An integer between 0 and 23 representing an hour within a day.

weekday
     At least the first two characters of an English day word.

spaces
     Any amount or no amount of whitespace.

sign
     An optional positive or negative sign.

trailer
     All formats accept an optional whitespace trailer.

The date input formats are strung together from the above pieces.  On output, the date formats are always printed in a single canonical manner, based on field width.  The date input and output formats are described below:

DATEw: 9 <= iw,ow <= 40
     Date format. Input format: leader + day + date-delimiter + month + date-delimiter + year + trailer.  Output format: DD-MMM-YY for W < 11, DD-MMM-YYYY otherwise.

EDATEw: 8 <= iw,ow <= 40
     European date format.  Input format same as DATE.  Output format: DD.MM.YY for W < 10, DD.MM.YYYY otherwise.

SDATEw: 8 <= iw,ow <= 40
     Standard date format. Input format: leader + year + date-delimiter + month + date-delimiter + day + trailer.  Output format: YY/MM/DD for W < 10, YYYY/MM/DD otherwise.

ADATEw: 8 <= iw,ow <= 40
     American date format.  Input format: leader + month + date-delimiter + day + date-delimiter + year + trailer.  Output format: MM/DD/YY for W < 10, MM/DD/YYYY otherwise.

JDATEw: 5 <= iw,ow <= 40
     Julian date format.  Input format: leader + julian + trailer.  Output format: YYDDD for W < 7, YYYYDDD otherwise.

QYRw: 4 <= iw <= 40, 6 <= ow <= 40
     Quarter/year format.  Input format: leader + quarter + q-delimiter + year + trailer.  Output format: Q Q YY, where the first Q is one of the digits 1, 2, 3, 4, if W < 8, Q Q YYYY otherwise.

MOYRw: 6 <= iw,ow <= 40
     Month/year format.  Input format: leader + month + date-delimiter + year + trailer.  Output format: MMM YY for W < 8, MMM YYYY otherwise.

WKYRw: 6 <= iw <= 40, 8 <= ow <= 40
     Week/year format.  Input format: leader + week + wk-delimiter + year + trailer.  Output format: WW WK YY for W < 10, WW WK YYYY otherwise.

DATETIMEw.d: 17 <= iw,ow <= 40
     Date and time format.  Input format: leader + day + date-delimiter + month + date-delimiter + yaer + time-delimiter + hour24 + time-delimiter + minute + opt-second.  Output format: DD-MMM-YYYY HH:MM.  If W > 19 then seconds :SS is added.  If W > 22 and D > 0 then fractional seconds .SS are added.

TIMEw.d: 5 <= iw,ow <= 40
     Time format.  Input format: leader + sign + spaces + hour + time-delimiter + minute + opt-second.  Output format: HH:MM. Seconds and fractional seconds are available with W of at least 8 and 10, respectively.

DTIMEw.d: 1 <= iw <= 40, 8 <= ow <= 40
     Time format with day count.  Input format: leader + sign + spaces + day-count + time-delimiter + hour + time-delimiter + minute + opt-second.  Output format: DD HH:MM.  Seconds and fractional seconds are available with W of at least 8 and 10, respectively.

WKDAYw: 2 <= iw,ow <= 40
     A weekday as a number between 1 and 7, where 1 is Sunday.  Input format: leader + weekday + trailer.  Output format: as many characters, in all capital letters, of the English name of the weekday as will fit in the field width.

MONTHw: 3 <= iw,ow <= 40
     A month as a number between 1 and 12, where 1 is January.  Input format: leader + month + trailer.  Output format: as many character, in all capital letters, of the English name of the month as will fit in the field width.

There are only two formats that may be used with string variables:

Aw: 1 <= iw <= 255, 1 <= ow <= 254
     The entire field is treated as a string value.

AHEXw => A: 2 <= iw <= 254; 2 <= ow <= 510
     The field is composed of characters in a string encoded as textual hex digit pairs.

     The default output W is half the input W.

Scratch Variables
-----------------

Most of the time, variables don't retain their values between cases. Instead, either they're being read from a data file or the active file, in which case they assume the value read, or, if created with COMPUTE or another transformation, they're initialized to the system-missing value or to blanks, depending on type.

However, sometimes it's useful to have a variable that keeps its value between cases.  You can do this with LEAVE (see LEAVE), or you can use a scratch variable.  Scratch variables are variables whose names begin with an octothorpe (#).

Scratch variables have the same properties as variables left with LEAVE: they retain their values between cases, and for the first case they are initialized to 0 or blanks.  They have the additional property that they are deleted before the execution of any procedure.  For this reason, scratch variables can't be used for analysis.  To obtain the same effect, use COMPUTE (see COMPUTE) to copy the scratch variable's value into an ordinary variable, then analysis that variable.

Files Used by PSPP
==================

PSPP makes use of many files each time it runs.  Some of these it reads, some it writes, some it creates.  Here is a table listing the most important of these files:

command file
syntax file
     These names (synonyms) refer to the file that contains instructions to PSPP that tell it what to do.  The syntax file's name is specified on the PSPP command line.  Syntax files can also be pulled in with INCLUDE (see INCLUDE).

data file
     Data files contain raw data in ASCII format suitable for being read in by DATA LIST.  Data can be embedded in the syntax file with BEGIN DATA and END DATA: this makes the syntax file a data file too.

listing file
     One or more output files are created by PSPP each time it is run.  The output files receive the tables and charts produced by statistical procedures.  The output files may be in any number of formats, depending on how PSPP is configured.

active file
     The active file is the ``file'' on which all PSPP procedures are performed.  The active file contains variable definitions and cases.  The active file is not necessarily a disk file: it is stored in memory if there is room.

Backus-Naur Form
================

The syntax of some parts of the PSPP language is presented in this manual using the formalism known as Backus-Naur Form, or BNF. The following table describes BNF:

  * Words in all-uppercase are PSPP keyword tokens.  In BNF, these are often called terminals.  There are some special terminals, which are actually written in lowercase for clarity:

     number
          A real number.

     integer
          An integer number.

     string
          A string.

     var-name
          A single variable name.

     =, /, +, -, etc.
          Operators and punctuators.

     .
          The terminal dot.  This is not necessarily an actual dot in the syntax file: see Commands, for more details.

  * Other words in all lowercase refer to BNF definitions, called productions.  These productions are also known as nonterminals.  Some nonterminals are very common, so they are defined here in English for clarity:

     var-list
          A list of one or more variable names or the keyword ALL.

     expression
          An expression.  See Expressions, for details.

  * ::= means ``is defined as''.  The left side of ::= gives the name of the nonterminal being defined.  The right side of ::= gives the definition of that nonterminal.  If the right side is empty, then one possible expansion of that nonterminal is nothing.  A BNF definition is called a production.

  * So, the key difference between a terminal and a nonterminal is that a terminal cannot be broken into smaller parts---in fact, every terminal is a single token (see Tokens).  On the other hand, nonterminals are composed of a (possibly empty) sequence of terminals and nonterminals. Thus, terminals indicate the deepest level of syntax description.  (In parsing theory, terminals are the leaves of the parse tree; nonterminals form the branches.)

  * The first nonterminal defined in a set of productions is called the start symbol.  The start symbol defines the entire syntax for that command.

Mathematical Expressions
************************

Some PSPP commands use expressions, which share a common syntax among all PSPP commands.  Expressions are made up of operands, which can be numbers, strings, or variable names, separated by operators.  There are five types of operators: grouping, arithmetic, logical, relational, and functions.

Every operator takes one or more arguments as input and produces or returns exactly one result as output.  Both strings and numeric values can be used as arguments and are produced as results, but each operator accepts only specific combinations of numeric and string values as arguments.  With few exceptions, operator arguments may be full-fledged expressions in themselves.

Boolean values
==============

There is a third type for arguments and results, the Boolean type, which is used to represent true/false conditions.  Booleans have only three possible values: 0 (false), 1 (true), and system-missing. System-missing is neither true nor false.

  * A numeric expression that has value 0, 1, or system-missing may be used in place of a Boolean.  Thus, the expression 0 AND 1 is valid (although it is always false).

  * A numeric expression with any other value will cause an error if it is used as a Boolean.  So, 2 OR 3 is invalid.

  * A Boolean expression may not be used in place of a numeric expression. Thus, (1>2) + (3<4) is invalid.

  * Strings and Booleans are not compatible, and neither may be used in place of the other.

Missing Values in Expressions
=============================

String missing values are not treated specially in expressions.  Most numeric operators return system-missing when given system-missing arguments.  Exceptions are listed under particular operator descriptions.

User-missing values for numeric variables are always transformed into the system-missing value, except inside the arguments to the VALUE, SYSMIS, and MISSING functions.

The missing-value functions can be used to precisely control how missing values are treated in expressions.  See Missing Value Functions, for more details.

Grouping Operators
==================

Parentheses (()) are the grouping operators.  Surround an expression with parentheses to force early evaluation.

Parentheses also surround the arguments to functions, but in that situation they act as punctuators, not as operators.

Arithmetic Operators
====================

The arithmetic operators take numeric arguments and produce numeric results.

A + B
     Adds A and B, returning the sum.

A - B
     Subtracts B from A, returning the difference.

A * B
     Multiplies A and B, returning the product.

A / B
     Divides A by B, returning the quotient.  If B is zero, the result is system-missing.

A ** B
     Returns the result of raising A to the power B.  If A is negative and B is not an integer, the result is system-missing.  The result of 0**0 is system-missing as well.

- A
     Reverses the sign of A.

Logical Operators
=================

The logical operators take logical arguments and produce logical results, meaning ``true or false''.  PSPP logical operators are not true Boolean operators because they may also result in a system-missing value.

A AND B
A & B
     True if both A and B are true.  However, if one argument is false and the other is missing, the result is false, not missing.  If both arguments are missing, the result is missing.

A OR B
A | B
     True if at least one of A and B is true.  If one argument is true and the other is missing, the result is true, not missing.  If both arguments are missing, the result is missing.

NOT A
~ A
     True if A is false.

Relational Operators
====================

The relational operators take numeric or string arguments and produce Boolean results.

Note that, with numeric arguments, PSPP does not make exact relational tests.  Instead, two numbers are considered to be equal even if they differ by a small amount.  This amount, epsilon, is dependent on the PSPP configuration and determined at compile time.  (The default value is 0.000000001, or 10**(-9).) Use of epsilon allows for round-off errors.  Use of epsilon is also idiotic, but the author is not a numeric analyst.

Strings cannot be compared to numbers.  When strings of different lengths are compared, the shorter string is right-padded with spaces to match the length of the longer string.

The results of string comparisons, other than tests for equality or inequality, are dependent on the character set in use.  String comparisons are case-sensitive.

A EQ B
A = B
     True if A is equal to B.

A LE B
A <= B
     True if A is less than or equal to B.

A LT B
A < B
     True if A is less than B.

A GE B
A >= B
     True if A is greater than or equal to B.

A GT B
A > B
     True if A is greater than B.

A NE B
A ~= B
A <> B
     True is A is not equal to B.

Functions
=========

PSPP functions provide mathematical abilities above and beyond those possible using simple operators.  Functions have a common syntax: each is composed of a function name followed by a left parenthesis, one or more arguments, and a right parenthesis.  Function names are not reserved; their names are specially treated only when followed by a left parenthesis: EXP(10) refers to the constant value e raised to the 10th power, but EXP by itself refers to the value of variable EXP.

The sections below describe each function in detail.

Advanced Mathematical Functions
-------------------------------

Advanced mathematical functions take numeric arguments and produce numeric results.

 -- Function: EXP (EXPONENT)
     Returns e (approximately 2.71828) raised to power EXPONENT.

 -- Function: LG10 (NUMBER)
     Takes the base-10 logarithm of NUMBER.  If NUMBER is not positive, the result is system-missing.

 -- Function: LN (NUMBER)
     Takes the base-e logarithm of NUMBER.  If NUMBER is not positive, the result is system-missing.

 -- Function: SQRT (NUMBER)
     Takes the square root of NUMBER.  If NUMBER is negative, the result is system-missing.

Miscellaneous Mathematical Functions
------------------------------------

Miscellaneous mathematical functions take numeric arguments and produce numeric results.

 -- Function: ABS (NUMBER)
     Results in the absolute value of NUMBER.

 -- Function: MOD (NUMERATOR, DENOMINATOR)
     Returns the remainder (modulus) of NUMERATOR divided by DENOMINATOR.  If DENOMINATOR is 0, the result is system-missing.  However, if NUMERATOR is 0 and DENOMINATOR is system-missing, the result is 0.

 -- Function: MOD10 (NUMBER)
     Returns the remainder when NUMBER is divided by 10.  If NUMBER is negative, MOD10(NUMBER) is negative or zero.

 -- Function: RND (NUMBER)
     Takes the absolute value of NUMBER and rounds it to an integer. Then, if NUMBER was negative originally, negates the result.

 -- Function: TRUNC (NUMBER)
     Discards the fractional part of NUMBER; that is, rounds NUMBER towards zero.

Trigonometric Functions
-----------------------

Trigonometric functions take numeric arguments and produce numeric results.

 -- Function: ACOS (NUMBER)
 -- Function: ARCOS (NUMBER)
     Takes the arccosine, in radians, of NUMBER.  Results in system-missing if NUMBER is not between -1 and 1.  Portability: none.

 -- Function: ARSIN (NUMBER)
     Takes the arcsine, in radians, of NUMBER.  Results in system-missing if NUMBER is not between -1 and 1 inclusive.

 -- Function: ARTAN (NUMBER)
     Takes the arctangent, in radians, of NUMBER.

 -- Function: ASIN (NUMBER)
     Takes the arcsine, in radians, of NUMBER.  Results in system-missing if NUMBER is not between -1 and 1 inclusive. Portability: none.

 -- Function: ATAN (NUMBER)
     Takes the arctangent, in radians, of NUMBER.

     Please note: Use of the AR* group of inverse trigonometric functions is recommended over the A* group because they are more portable.

 -- Function: COS (ANGLE)
     Takes the cosine of ANGLE which should be in radians.

 -- Function: SIN (ANGLE)
     Takes the sine of ANGLE which should be in radians.

 -- Function: TAN (ANGLE)
     Takes the tangent of ANGLE which should be in radians. Results in system-missing at values of ANGLE that are too close to odd multiples of pi/2. Portability: none.

Missing-Value Functions
-----------------------

Missing-value functions take various types as arguments, returning various types of results.

 -- Function: MISSING (VARIABLE OR EXPRESSION)
     NUM may be a single variable name or an expression.  If it is a variable name, results in 1 if the variable has a user-missing or system-missing value for the current case, 0 otherwise.  If it is an expression, results in 1 if the expression has the system-missing value, 0 otherwise.

          Please note: If the argument is a string expression other than a variable name, MISSING is guaranteed to return 0, because strings do not have a system-missing value.  Also, when using a numeric expression argument, remember that user-missing values are converted to the system-missing value in most contexts.  Thus, the expressions MISSING(VAR1 OP VAR2) and MISSING(VAR1) OR MISSING(VAR2) are often equivalent, depending on the specific operator OP used.

 -- Function: NMISS (EXPR [, EXPR]...)
     Each argument must be a numeric expression.  Returns the number of user- or system-missing values in the list.  As a special extension, the syntax VAR1 TO VAR2 may be used to refer to a range of variables; see Sets of Variables, for more details.

 -- Function: NVALID (EXPR [, EXPR]...)
     Each argument must be a numeric expression.  Returns the number of values in the list that are not user- or system-missing.  As a special extension, the syntax VAR1 TO VAR2 may be used to refer to a range of variables; see Sets of Variables, for more details.

 -- Function: SYSMIS (VARIABLE OR EXPRESSION)
     When given the name of a numeric variable, returns 1 if the value of that variable is system-missing.  Otherwise, if the value is not missing or if it is user-missing, returns 0.  If given the name of a string variable, always returns 1.  If given an expression other than a single variable name, results in 1 if the value is system- or user-missing, 0 otherwise.

 -- Function: VALUE (VARIABLE)
     Prevents the user-missing values of VARIABLE from being transformed into system-missing values: If VARIABLE is not system- or user-missing, results in the value of VARIABLE.  If VARIABLE is user-missing, results in the value of VARIABLE anyway.  If VARIABLE is system-missing, results in system-missing.

Pseudo-Random Number Generation Functions
-----------------------------------------

Pseudo-random number generation functions take numeric arguments and produce numeric results.

PSPP uses the alleged RC4 cipher as a pseudo-random number generator (PRNG).  The bytes output by this PRNG are system-independent for a given random seed, but differences in endianness and floating-point formats will make PRNG results differ from system to system.  RC4 should produce high-quality random numbers for simulation purposes. (If you're concerned about the quality of the random number generator, well, you're using a statistical processing package---analyze it!)

PSPP's implementation of RC4 has not undergone any security auditing. Furthermore, various precautions that would be necessary for secure operation, such as secure seeding and discarding the first several bytes of output, have not been taken.  Therefore, PSPP's implementation of RC4 should not be used for security purposes.

 -- Function: NORMAL (NUMBER)
     Results in a random number.  Results from NORMAL are normally distributed with a mean of 0 and a standard deviation of NUMBER.

 -- Function: UNIFORM (NUMBER)
     Results in a random number between 0 and NUMBER.  Results from UNIFORM are evenly distributed across its entire range.  There may be a maximum on the largest random number ever generated---this is often 2**31-1 (2,147,483,647), but it may be orders of magnitude higher or lower.

Set-Membership Functions
------------------------

Set membership functions determine whether a value is a member of a set. They take a set of numeric arguments or a set of string arguments, and produce Boolean results.

String comparisons are performed according to the rules given in Relational Operators.

 -- Function: ANY (VALUE, SET [, SET]...)
     Results in true if VALUE is equal to any of the SET values.  Otherwise, results in false.  If VALUE is system-missing, returns system-missing.  System-missing values in SET do not cause ANY to return system-missing.

 -- Function: RANGE (VALUE, LOW, HIGH [, LOW, HIGH]...)
     Results in true if VALUE is in any of the intervals bounded by LOW and HIGH inclusive.  Otherwise, results in false. Each LOW must be less than or equal to its corresponding HIGH value.  LOW and HIGH must be given in pairs. If VALUE is system-missing, returns system-missing. System-missing values in SET do not cause RANGE to return system-missing.

Statistical Functions
---------------------

Statistical functions compute descriptive statistics on a list of values.  Some statistics can be computed on numeric or string values; other can only be computed on numeric values.  Their results have the same type as their arguments.  The current case's weighting factor (see WEIGHT) has no effect on statistical functions.

With statistical functions it is possible to specify a minimum number of non-missing arguments for the function to be evaluated.  To do so, append a dot and the number to the function name.  For instance, to specify a minimum of three valid arguments to the MEAN function, use the name MEAN.3.

 -- Function: CFVAR (NUMBER, NUMBER[, ...])
     Results in the coefficient of variation of the values of NUMBER. This function requires at least two valid arguments to give a non-missing result.  (The coefficient of variation is the standard deviation divided by the mean.)

 -- Function: MAX (VALUE, VALUE[, ...])
     Results in the value of the greatest VALUE.  The VALUEs may be numeric or string.  Although at least two arguments must be given, only one need be valid for MAX to give a non-missing result.

 -- Function: MEAN (NUMBER, NUMBER[, ...])
     Results in the mean of the values of NUMBER.  Although at least two arguments must be given, only one need be valid for MEAN to give a non-missing result.

 -- Function: MIN (NUMBER, NUMBER[, ...])
     Results in the value of the least VALUE.  The VALUEs may be numeric or string.  Although at least two arguments must be given, only one need be valid for MAX to give a non-missing result.

 -- Function: SD (NUMBER, NUMBER[, ...])
     Results in the standard deviation of the values of NUMBER. This function requires at least two valid arguments to give a non-missing result.

 -- Function: SUM (NUMBER, NUMBER[, ...])
     Results in the sum of the values of NUMBER.  Although at least two arguments must be given, only one need by valid for SUM to give a non-missing result.

 -- Function: VAR (NUMBER, NUMBER[, ...])
     Results in the variance of the values of NUMBER.  This function requires at least two valid arguments to give a non-missing result.

 -- Function: VARIANCE (NUMBER, NUMBER[, ...])
     Results in the variance of the values of NUMBER.  This function requires at least two valid arguments to give a non-missing result. (Use VAR in preference to VARIANCE for reasons of portability.)

String Functions
----------------

String functions take various arguments and return various results.

 -- Function: CONCAT (STRING, STRING[, ...])
     Returns a string consisting of each STRING in sequence. CONCAT("abc", "def", "ghi") has a value of "abcdefghi". The resultant string is truncated to a maximum of 255 characters.

 -- Function: INDEX (HAYSTACK, NEEDLE)
     Returns a positive integer indicating the position of the first occurrence NEEDLE in HAYSTACK.  Returns 0 if HAYSTACK does not contain NEEDLE.  Returns system-missing if NEEDLE is an empty string.

 -- Function: INDEX (HAYSTACK, NEEDLE, DIVISOR)
     Divides NEEDLE into parts, each with length DIVISOR. Searches HAYSTACK for the first occurrence of each part, and returns the smallest value.  Returns 0 if HAYSTACK does not contain any part in NEEDLE.  It is an error if DIVISOR cannot be evenly divided into the length of NEEDLE.  Returns system-missing if NEEDLE is an empty string.

 -- Function: LENGTH (STRING)
     Returns the number of characters in STRING.

 -- Function: LOWER (STRING)
     Returns a string identical to STRING except that all uppercase letters are changed to lowercase letters.  The definitions of ``uppercase'' and ``lowercase'' are system-dependent.

 -- Function: LPAD (STRING, LENGTH)
     If STRING is at least LENGTH characters in length, returns STRING unchanged.  Otherwise, returns STRING padded with spaces on the left side to length LENGTH.  Returns an empty string if LENGTH is system-missing, negative, or greater than 255.

 -- Function: LPAD (STRING, LENGTH, PADDING)
     If STRING is at least LENGTH characters in length, returns STRING unchanged.  Otherwise, returns STRING padded with PADDING on the left side to length LENGTH.  Returns an empty string if LENGTH is system-missing, negative, or greater than 255, or if PADDING does not contain exactly one character.

 -- Function: LTRIM (STRING)
     Returns STRING, after removing leading spaces.  Other whitespace, such as tabs, carriage returns, line feeds, and vertical tabs, is not removed.

 -- Function: LTRIM (STRING, PADDING)
     Returns STRING, after removing leading PADDING characters. If PADDING does not contain exactly one character, returns an empty string.

 -- Function: NUMBER (STRING)
     Returns the number produced when STRING is interpreted according to format FX.0, where X is the number of characters in STRING.  If STRING does not form a proper number, system-missing is returned without an error message.  Portability: none.

 -- Function: NUMBER (STRING, FORMAT)
     Returns the number produced when STRING is interpreted according to format specifier FORMAT.  Only the number of characters in STRING specified by FORMAT are examined.  For example, NUMBER("123", F3.0) and NUMBER("1234", F3.0) both have value 123.  If STRING does not form a proper number, system-missing is returned without an error message.

 -- Function: RINDEX (STRING, FORMAT)
     Returns a positive integer indicating the position of the last occurrence of NEEDLE in HAYSTACK.  Returns 0 if HAYSTACK does not contain NEEDLE.  Returns system-missing if NEEDLE is an empty string.

 -- Function: RINDEX (HAYSTACK, NEEDLE, DIVISOR)
     Divides NEEDLE into parts, each with length DIVISOR. Searches HAYSTACK for the last occurrence of each part, and returns the largest value.  Returns 0 if HAYSTACK does not contain any part in NEEDLE.  It is an error if DIVISOR cannot be evenly divided into the length of NEEDLE.  Returns system-missing if NEEDLE is an empty string.

 -- Function: RPAD (STRING, LENGTH)
     If STRING is at least LENGTH characters in length, returns STRING unchanged.  Otherwise, returns STRING padded with spaces on the right to length LENGTH.  Returns an empty string if LENGTH is system-missing, negative, or greater than 255.

 -- Function: RPAD (STRING, LENGTH, PADDING)
     If STRING is at least LENGTH characters in length, returns STRING unchanged.  Otherwise, returns STRING padded with PADDING on the right to length LENGTH.  Returns an empty string if LENGTH is system-missing, negative, or greater than 255, or if PADDING does not contain exactly one character.

 -- Function: RTRIM (STRING)
     Returns STRING, after removing trailing spaces.  Other types of whitespace are not removed.

 -- Function: RTRIM (STRING, PADDING)
     Returns STRING, after removing trailing PADDING characters. If PADDING does not contain exactly one character, returns an empty string.

 -- Function: STRING (NUMBER, FORMAT)
     Returns a string corresponding to NUMBER in the format given by format specifier FORMAT.  For example, STRING(123.56, F5.1) has the value "123.6".

 -- Function: SUBSTR (STRING, START)
     Returns a string consisting of the value of STRING from position START onward.  Returns an empty string if START is system-missing or has a value less than 1 or greater than the number of characters in STRING.

 -- Function: SUBSTR (STRING, START, COUNT)
     Returns a string consisting of the first COUNT characters from STRING beginning at position START.  Returns an empty string if START or COUNT is system-missing, if START is less than 1 or greater than the number of characters in STRING, or if COUNT is less than 1.  Returns a string shorter than COUNT characters if START + COUNT - 1 is greater than the number of characters in STRING.  Examples: SUBSTR("abcdefg", 3, 2) has value "cd"; SUBSTR("Ben Pfaff", 5, 10) has the value "Pfaff".

 -- Function: UPCASE (STRING)
     Returns STRING, changing lowercase letters to uppercase letters.

Time & Date Functions
---------------------

The legal range of dates for use in PSPP is 15 Oct 1582 through 31 Dec 19999.

     Please note: Most time & date extraction functions will accept invalid arguments:

       * Negative numbers in PSPP time format.

       * Numbers less than 86,400 in PSPP date format.

     However, sensible results are not guaranteed for these invalid values. The given equivalents for these functions are definitely not guaranteed for invalid values.

     Please note also: The time & date construction functions do produce reasonable and useful results for out-of-range values; these are not considered invalid.

How times & dates are defined and represented
.............................................

Times and dates are handled by PSPP as single numbers.  A time is an interval.  PSPP measures times in seconds. Thus, the following intervals correspond with the numeric values given:

               10 minutes                        600
               1 hour                          3,600
               1 day, 3 hours, 10 seconds     97,210
               40 days                     3,456,000
               10010 d, 14 min, 24 s     864,864,864

A date, on the other hand, is a particular instant in the past or the future.  PSPP represents a date as a number of seconds after the midnight that separated 8 Oct 1582 and 9 Oct 1582.  (Please note that 15 Oct 1582 immediately followed 9 Oct 1582.)  Thus, the midnights before the dates given below correspond with the numeric PSPP dates given:

                   15 Oct 1582                86,400
                    4 Jul 1776         6,113,318,400
                    1 Jan 1900        10,010,390,400
                    1 Oct 1978        12,495,427,200
                   24 Aug 1995        13,028,601,600

Please note:

  * A time may be added to, or subtracted from, a date, resulting in a date.

  * The difference of two dates may be taken, resulting in a time.

  * Two times may be added to, or subtracted from, each other, resulting in a time.

(Adding two dates does not produce a useful result.)

Since times and dates are merely numbers, the ordinary addition and subtraction operators are employed for these purposes.

     Please note: Many dates and times have extremely large values---just look at the values above.  Thus, it is not a good idea to take powers of these values; also, the accuracy of some procedures may be affected.  If necessary, convert times or dates in seconds to some other unit, like days or years, before performing analysis.

Functions that Produce Times
............................

These functions take numeric arguments and produce numeric results in PSPP time format.

 -- Function: TIME.DAYS (NDAYS)
     Results in a time value corresponding to NDAYS days. (TIME.DAYS(X) is equivalent to X * 60 * 60 * 24.)

 -- Function: TIME.HMS (NHOURS, NMINS, NSECS)
     Results in a time value corresponding to NHOURS hours, NMINS minutes, and NSECS seconds.  (TIME.HMS(H, M, S) is equivalent to H*60*60 + M*60 + S.)

Functions that Examine Times
............................

These functions take numeric arguments in PSPP time format and give numeric results.

 -- Function: CTIME.DAYS (TIME)
     Results in the number of days and fractional days in TIME. (CTIME.DAYS(X) is equivalent to X/60/60/24.)

 -- Function: CTIME.HOURS (TIME)
     Results in the number of hours and fractional hours in TIME. (CTIME.HOURS(X) is equivalent to X/60/60.)

 -- Function: CTIME.MINUTES (TIME)
     Results in the number of minutes and fractional minutes in TIME. (CTIME.MINUTES(X) is equivalent to X/60.)

 -- Function: CTIME.SECONDS (TIME)
     Results in the number of seconds and fractional seconds in TIME. (CTIME.SECONDS does nothing; CTIME.SECONDS(X) is equivalent to X.)

Functions that Produce Dates
............................

These functions take numeric arguments and give numeric results in the PSPP date format.  Arguments taken by these functions are:

day
     Refers to a day of the month between 1 and 31.

month
     Refers to a month of the year between 1 and 12.

quarter
     Refers to a quarter of the year between 1 and 4.  The quarters of the year begin on the first days of months 1, 4, 7, and 10.

week
     Refers to a week of the year between 1 and 53.

yday
     Refers to a day of the year between 1 and 366.

year
     Refers to a year between 1582 and 19999.

If these functions' arguments are out-of-range, they are correctly normalized before conversion to date format.  Non-integers are rounded toward zero.

 -- Function: DATE.DMY (DAY, MONTH, YEAR)
 -- Function: DATE.MDY (MONTH, DAY, YEAR)
     Results in a date value corresponding to the midnight before day DAY of month MONTH of year YEAR.

 -- Function: DATE.MOYR (MONTH, YEAR)
     Results in a date value corresponding to the midnight before the first day of month MONTH of year YEAR.

 -- Function: DATE.QYR (QUARTER, YEAR)
     Results in a date value corresponding to the midnight before the first day of quarter QUARTER of year YEAR.

 -- Function: DATE.WKYR (WEEK, YEAR)
     Results in a date value corresponding to the midnight before the first day of week WEEK of year YEAR.

 -- Function: DATE.YRDAY (YEAR, YDAY)
     Results in a date value corresponding to the midnight before day YDAY of year YEAR.

Functions that Examine Dates
............................

These functions take numeric arguments in PSPP date or time format and give numeric results.  These names are used for arguments:

date
     A numeric value in PSPP date format.

time
     A numeric value in PSPP time format.

time-or-date
     A numeric value in PSPP time or date format.

 -- Function: XDATE.DATE (TIME-OR-DATE)
     For a time, results in the time corresponding to the number of whole days DATE-OR-TIME includes.  For a date, results in the date corresponding to the latest midnight at or before DATE-OR-TIME; that is, gives the date that DATE-OR-TIME is in. (XDATE.DATE(X) is equivalent to TRUNC(X/86400)*86400.) Applying this function to a time is a non-portable feature.

 -- Function: XDATE.HOUR (TIME-OR-DATE)
     For a time, results in the number of whole hours beyond the number of whole days represented by DATE-OR-TIME.  For a date, results in the hour (as an integer between 0 and 23) corresponding to DATE-OR-TIME.  (XDATE.HOUR(X) is equivalent to MOD(TRUNC(X/3600),24))  Applying this function to a time is a non-portable feature.

 -- Function: XDATE.JDAY (DATE)
     Results in the day of the year (as an integer between 1 and 366) corresponding to DATE.

 -- Function: XDATE.MDAY (DATE)
     Results in the day of the month (as an integer between 1 and 31) corresponding to DATE.

 -- Function: XDATE.MINUTE (TIME-OR-DATE)
     Results in the number of minutes (as an integer between 0 and 59) after the last hour in TIME-OR-DATE.  (XDATE.MINUTE(X) is equivalent to MOD(TRUNC(X/60),60)) Applying this function to a time is a non-portable feature.

 -- Function: XDATE.MONTH (DATE)
     Results in the month of the year (as an integer between 1 and 12) corresponding to DATE.

 -- Function: XDATE.QUARTER (DATE)
     Results in the quarter of the year (as an integer between 1 and 4) corresponding to DATE.

 -- Function: XDATE.SECOND (TIME-OR-DATE)
     Results in the number of whole seconds after the last whole minute (as an integer between 0 and 59) in TIME-OR-DATE. (XDATE.SECOND(X) is equivalent to MOD(X, 60).)  Applying this function to a time is a non-portable feature.

 -- Function: XDATE.TDAY (TIME)
     Results in the number of whole days (as an integer) in TIME. (XDATE.TDAY(X) is equivalent to TRUNC(X/86400).)

 -- Function: XDATE.TIME (DATE)
     Results in the time of day at the instant corresponding to DATE, in PSPP time format.  This is the number of seconds since midnight on the day corresponding to DATE.  (XDATE.TIME(X) is equivalent to TRUNC(X/86400)*86400.)

 -- Function: XDATE.WEEK (DATE)
     Results in the week of the year (as an integer between 1 and 53) corresponding to DATE.

 -- Function: XDATE.WKDAY (DATE)
     Results in the day of week (as an integer between 1 and 7) corresponding to DATE.  The days of the week are:

     1
          Sunday

     2
          Monday

     3
          Tuesday

     4
          Wednesday

     5
          Thursday

     6
          Friday

     7
          Saturday

 -- Function: XDATE.YEAR (DATE)
     Returns the year (as an integer between 1582 and 19999) corresponding to DATE.

Miscellaneous Functions
-----------------------

Miscellaneous functions take various arguments and produce various results.

 -- Function: LAG (VARIABLE)
     VARIABLE must be a numeric or string variable name.  LAG results in the value of that variable for the case before the current one.  In case-selection procedures, LAG results in the value of the variable for the last case selected.  Results in system-missing (for numeric variables) or blanks (for string variables) for the first case or before any cases are selected.

 -- Function: LAG (VARIABLE, NCASES)
     VARIABLE must be a numeric or string variable name.  NCASES must be a small positive constant integer, although there is no explicit limit.  (Use of a large value for NCASES will increase memory consumption, since PSPP must keep NCASES cases in memory.) LAG (VARIABLE, NCASES results in the value of VARIABLE that is NCASES before the case currently being processed.  See LAG (VARIABLE) above for more details.

 -- Function: YRMODA (YEAR, MONTH, DAY)
     YEAR is a year between 0 and 199 or 1582 and 19999.  MONTH is a month between 1 and 12.  DAY is a day between 1 and 31.  If MONTH or DAY is out-of-range, it changes the next higher unit.  For instance, a DAY of 0 refers to the last day of the previous month, and a MONTH of 13 refers to the first month of the next year.  YEAR must be in range.  If YEAR is between 0 and 199, 1900 is added.  YEAR, MONTH, and DAY must all be integers.

     YRMODA results in the number of days between 15 Oct 1582 and the date specified, plus one.  The date passed to YRMODA must be on or after 15 Oct 1582.  15 Oct 1582 has a value of 1.

Functions Not Implemented
-------------------------

These functions are not yet implemented and thus not yet documented, since it's a hassle.

  * CDF.xxx

  * CDFNORM

  * IDF.xxx

  * NCDF.xxx

  * PROBIT

  * RV.xxx

Operator Precedence
===================

The following table describes operator precedence.  Smaller-numbered levels in the table have higher precedence.  Within a level, operations are performed from left to right, except for level 2 (exponentiation), where operations are performed from right to left.  If an operator appears in the table in two places (-), the first occurrence is unary, the second is binary.

 1. (  )

 2. **

 3. -

 4. *  /

 5. +  -

 6. EQ  GE  GT  LE  LT  NE

 7. AND  NOT  OR

Data Input and Output
*********************

Data are the focus of the PSPP language. Each datum  belongs to a case (also called an observation). Each case represents an individual or `experimental unit'. For example, in the results of a survey, the names of the respondents, their sex, age etc. and their responses are all data and the data pertaining to single respondent is a case. This chapter examines the PSPP commands for defining variables and reading and writing data.

     Please note: Data is not actually read until a procedure is executed.  These commands tell PSPP how to read data, but they do not cause PSPP to read data.

BEGIN DATA
==========

     BEGIN DATA.
     ...
     END DATA.

BEGIN DATA and END DATA can be used to embed raw ASCII data in a PSPP syntax file.  DATA LIST or another input procedure must be used before BEGIN DATA (see DATA LIST). BEGIN DATA and END DATA must be used together.  END
DATA must appear by itself on a single line, with no leading whitespace and exactly one space between the words END and DATA, followed immediately by the terminal dot, like this:

     END DATA.

CLEAR TRANSFORMATIONS
=====================

     CLEAR TRANSFORMATIONS.

CLEAR TRANSFORMATIONS clears out all pending transformations.  It does not cancel the current input program.  It is valid only when PSPP is interactive, not in syntax files.

DATA LIST
=========

Used to read text or binary data, DATA LIST is the most fundamental data-reading command.  Even the more sophisticated input methods use DATA LIST commands as a building block. Understanding DATA LIST is important to understanding how to use PSPP to read your data files.

There are two major variants of DATA LIST, which are fixed format and free format.  In addition, free format has a minor variant, list format, which is discussed in terms of its differences from vanilla free format.

Each form of DATA LIST is described in detail below.

DATA LIST FIXED
---------------

     DATA LIST [FIXED]
             {TABLE,NOTABLE}
             FILE='filename'
             RECORDS=record_count
             END=end_var
             /[line_no] var_spec...

     where each var_spec takes one of the forms
             var_list start-end [type_spec]
             var_list (fortran_spec)

DATA LIST FIXED is used to read data files that have values at fixed positions on each line of single-line or multiline records.  The keyword FIXED is optional.

The FILE subcommand must be used if input is to be taken from an external file.  It may be used to specify a filename as a string or a file handle (see FILE HANDLE).  If the FILE subcommand is not used, then input is assumed to be specified within the command file using BEGIN DATA...END DATA (see BEGIN DATA).

The optional RECORDS subcommand, which takes a single integer as an argument, is used to specify the number of lines per record.  If RECORDS is not specified, then the number of lines per record is calculated from the list of variable specifications later in DATA LIST.

The END subcommand is only useful in conjunction with INPUT
PROGRAM.  See INPUT PROGRAM, for details.

DATA LIST can optionally output a table describing how the data file will be read.  The TABLE subcommand enables this output, and NOTABLE disables it.  The default is to output the table.

The list of variables to be read from the data list must come last. Each line in the data record is introduced by a slash (/). Optionally, a line number may follow the slash.  Following, any number of variable specifications may be present.

Each variable specification consists of a list of variable names followed by a description of their location on the input line.  Sets of variables may specified using the DATA LIST TO convention (see Sets of Variables).  There are two ways to specify the location of the variable on the line: PSPP style and FORTRAN style.

With PSPP style, the starting column and ending column for the field are specified after the variable name, separated by a dash (-). For instance, the third through fifth columns on a line would be specified 3-5.  By default, variables are considered to be in F format (see Input/Output Formats).  (This default can be changed; see SET for more information.)

When using PSPP style, to use a variable format other than the default, specify the format type in parentheses after the column numbers.  For instance, for alphanumeric A format, use (A).

In addition, implied decimal places can be specified in parentheses after the column numbers.  As an example, suppose that a data file has a field in which the characters 1234 should be interpreted as having the value 12.34.  Then this field has two implied decimal places, and the corresponding specification would be (2).  If a field that has implied decimal places contains a decimal point, then the implied decimal places are not applied.

Changing the variable format and adding implied decimal places can be done together; for instance, (N,5).

When using PSPP style, the input and output width of each variable is computed from the field width.  The field width must be evenly divisible into the number of variables specified.

FORTRAN style is an altogether different approach to specifying field locations.  With this approach, a list of variable input format specifications, separated by commas, are placed after the variable names inside parentheses.  Each format specifier advances as many characters into the input line as it uses.

In addition to the standard format specifiers (see Input/Output Formats), FORTRAN style defines some extensions:

X
     Advance the current column on this line by one character position.

TX
     Set the current column on this line to column X, with column numbers considered to begin with 1 at the left margin.

NEWRECX
     Skip forward X lines in the current record, resetting the active column to the left margin.

Repeat count
     Any format specifier may be preceded by a number.  This causes the action of that format specifier to be repeated the specified number of times.

(SPEC1, ..., SPECN)
     Group the given specifiers together.  This is most useful when preceded by a repeat count.  Groups may be nested arbitrarily.

FORTRAN and PSPP styles may be freely intermixed.  PSPP style leaves the active column immediately after the ending column specified.  Record motion using NEWREC in FORTRAN style also applies to later FORTRAN and PSPP specifiers.

Examples
........

 1. DATA LIST TABLE /NAME 1-10 (A) INFO1 TO INFO3 12-17 (1).

          BEGIN DATA.
          John Smith 102311
          Bob Arnold 122015
          Bill Yates  918 6
          END DATA.

     Defines the following variables:

       * NAME, a 10-character-wide long string variable, in columns 1 through 10.

       * INFO1, a numeric variable, in columns 12 through 13.

       * INFO2, a numeric variable, in columns 14 through 15.

       * INFO3, a numeric variable, in columns 16 through 17.

     The BEGIN DATA/END DATA commands cause three cases to be defined:

          Case   NAME         INFO1   INFO2   INFO3
             1   John Smith     10      23      11
             2   Bob Arnold     12      20      15
             3   Bill Yates      9      18       6

     The TABLE keyword causes PSPP to print out a table describing the four variables defined.

 2. DAT LIS FIL="survey.dat"
                  /ID 1-5 NAME 7-36 (A) SURNAME 38-67 (A) MINITIAL 69 (A)
                  /Q01 TO Q50 7-56
                  /.

     Defines the following variables:

       * ID, a numeric variable, in columns 1-5 of the first record.

       * NAME, a 30-character long string variable, in columns 7-36 of the first record.

       * SURNAME, a 30-character long string variable, in columns 38-67 of the first record.

       * MINITIAL, a 1-character short string variable, in column 69 of the first record.

       * Fifty variables Q01, Q02, Q03, ..., Q49, Q50, all numeric, Q01 in column 7, Q02 in column 8, ..., Q49 in column 55, Q50 in column 56, all in the second record.

     Cases are separated by a blank record.

     Data is read from file survey.dat in the current directory.

     This example shows keywords abbreviated to their first 3 letters.

DATA LIST FREE
--------------

     DATA LIST FREE
             [{NOTABLE,TABLE}]
             FILE='filename'
             END=end_var
             /var_spec...

     where each var_spec takes one of the forms
             var_list [(type_spec)]
             var_list *

In free format, the input data is structured as a series of comma- or whitespace-delimited fields (end of line is one form of whitespace; it is not treated specially).  Field contents may be surrounded by matched pairs of apostrophes (') or quotes ("), or they may be unenclosed.  For any type of field leading white space (up to the apostrophe or quote, if any) is not included in the field.

Multiple consecutive delimiters are equivalent to a single delimiter. To specify an empty field, write an empty set of single or double quotes; for instance, "".

The NOTABLE and TABLE subcommands are as in DATA LIST FIXED above. NOTABLE is the default.

The FILE and END subcommands are as in DATA LIST FIXED above.

The variables to be parsed are given as a single list of variable names. This list must be introduced by a single slash (/).  The set of variable names may contain format specifications in parentheses (see Input/Output Formats).  Format specifications apply to all variables back to the previous parenthesized format specification.

In addition, an asterisk may be used to indicate that all variables preceding it are to have input/output format F8.0.

Specified field widths are ignored on input, although all normal limits on field width apply, but they are honored on output.

DATA LIST LIST
--------------

     DATA LIST LIST
             [{NOTABLE,TABLE}]
             FILE='filename'
             END=end_var
             /var_spec...

     where each var_spec takes one of the forms
             var_list [(type_spec)]
             var_list *

With one exception, DATA LIST LIST is syntactically and semantically equivalent to DATA LIST FREE.  The exception is that each input line is expected to correspond to exactly one input record.  If more or fewer fields are found on an input line than expected, an appropriate diagnostic is issued.

END CASE
========

     END CASE.

END CASE is used only within INPUT PROGRAM to output the current case.  See INPUT PROGRAM, for details.

END FILE
========

     END FILE.

END FILE is used only within INPUT PROGRAM to terminate the current input program.  See INPUT PROGRAM.

FILE HANDLE
===========

     FILE HANDLE handle_name
             /NAME='filename'
             /RECFORM={VARIABLE,FIXED,SPANNED}
             /LRECL=rec_len
             /MODE={CHARACTER,IMAGE,BINARY,MULTIPUNCH,360}

Use FILE HANDLE to define the attributes of a file that does not use conventional variable-length records terminated by newline characters.

Specify the file handle name as an identifier.  Any given identifier may only appear once in a PSPP run.  File handles may not be reassigned to a different file.  The file handle name must immediately follow the FILE
HANDLE command name.

The NAME subcommand specifies the name of the file associated with the handle.  It is the only required subcommand.

The RECFORM subcommand specifies how the file is laid out.  VARIABLE specifies variable-length lines terminated with newlines, and it is the default.  FIXED specifies fixed-length records.  SPANNED is not supported.

LRECL specifies the length of fixed-length records.  It is required if /RECFORM FIXED is specified.

MODE specifies a file mode.  CHARACTER, the default, causes the data file to be opened in ANSI C text mode.  BINARY causes the data file to be opened in ANSI C binary mode.  The other possibilities are not supported.

INPUT PROGRAM
=============

     INPUT PROGRAM.
     ... input commands ...
     END INPUT PROGRAM.

INPUT PROGRAM...END INPUT PROGRAM specifies a complex input program.  By placing data input commands within INPUT
PROGRAM, PSPP programs can take advantage of more complex file structures than available with only DATA LIST.

The first sort of extended input program is to simply put multiple DATA
LIST commands within the INPUT PROGRAM.  This will cause all of the data files to be read in parallel.  Input will stop when end of file is reached on any of the data files.

Transformations, such as conditional and looping constructs, can also be included within INPUT PROGRAM.  These can be used to combine input from several data files in more complex ways.  However, input will still stop when end of file is reached on any of the data files.

To prevent INPUT PROGRAM from terminating at the first end of file, use the END subcommand on DATA LIST.  This subcommand takes a variable name, which should be a numeric scratch variable (see Scratch Variables). (It need not be a scratch variable but otherwise the results can be surprising.)  The value of this variable is set to 0 when reading the data file, or 1 when end of file is encountered.

Two additional commands are useful in conjunction with INPUT PROGRAM. END CASE is the first.  Normally each loop through the INPUT PROGRAM structure produces one case.  END CASE controls exactly when cases are output.  When END CASE is used, looping from the end of INPUT PROGRAM to the beginning does not cause a case to be output.

END FILE is the second.  When the END subcommand is used on DATA
LIST, there is no way for the INPUT PROGRAM construct to stop looping, so an infinite loop results.  END FILE, when executed, stops the flow of input data and passes out of the INPUT PROGRAM structure.

All this is very confusing.  A few examples should help to clarify.

     INPUT PROGRAM.
             DATA LIST NOTABLE FILE='a.data'/X 1-10.
             DATA LIST NOTABLE FILE='b.data'/Y 1-10.
     END INPUT PROGRAM.
     LIST.

The example above reads variable X from file a.data and variable Y from file b.data.  If one file is shorter than the other then the extra data in the longer file is ignored.

     INPUT PROGRAM.
             NUMERIC #A #B.

             DO IF NOT #A.
                     DATA LIST NOTABLE END=#A FILE='a.data'/X 1-10.
             END IF.
             DO IF NOT #B.
                     DATA LIST NOTABLE END=#B FILE='b.data'/Y 1-10.
             END IF.
             DO IF #A AND #B.
                     END FILE.
             END IF.
             END CASE.
     END INPUT PROGRAM.
     LIST.

The above example reads variable X from a.data and variable Y from b.data.  If one file is shorter than the other then the missing field is set to the system-missing value alongside the present value for the remaining length of the longer file.

     INPUT PROGRAM.
             NUMERIC #A #B.

             DO IF #A.
                     DATA LIST NOTABLE END=#B FILE='b.data'/X 1-10.
                     DO IF #B.
                             END FILE.
                     ELSE.
                             END CASE.
                     END IF.
             ELSE.
                     DATA LIST NOTABLE END=#A FILE='a.data'/X 1-10.
                     DO IF NOT #A.
                             END CASE.
                     END IF.
             END IF.
     END INPUT PROGRAM.
     LIST.

The above example reads data from file a.data, then from b.data, and concatenates them into a single active file.

     INPUT PROGRAM.
             NUMERIC #EOF.

             LOOP IF NOT #EOF.
                     DATA LIST NOTABLE END=#EOF FILE='a.data'/X 1-10.
                     DO IF NOT #EOF.
                             END CASE.
                     END IF.
             END LOOP.

             COMPUTE #EOF = 0.
             LOOP IF NOT #EOF.
                     DATA LIST NOTABLE END=#EOF FILE='b.data'/X 1-10.
                     DO IF NOT #EOF.
                             END CASE.
                     END IF.
             END LOOP.

             END FILE.
     END INPUT PROGRAM.
     LIST.

The above example does the same thing as the previous example, in a different way.

     INPUT PROGRAM.
             LOOP #I=1 TO 50.
                     COMPUTE X=UNIFORM(10).
                     END CASE.
             END LOOP.
             END FILE.
     END INPUT PROGRAM.
     LIST/FORMAT=NUMBERED.

The above example causes an active file to be created consisting of 50 random variates between 0 and 10.

LIST
====

     LIST
             /VARIABLES=var_list
             /CASES=FROM start_index TO end_index BY incr_index
             /FORMAT={UNNUMBERED,NUMBERED} {WRAP,SINGLE}
                     {NOWEIGHT,WEIGHT}

The LIST procedure prints the values of specified variables to the listing file.

The VARIABLES subcommand specifies the variables whose values are to be printed.  Keyword VARIABLES is optional.  If VARIABLES subcommand is not specified then all variables in the active file are printed.

The CASES subcommand can be used to specify a subset of cases to be printed.  Specify FROM and the case number of the first case to print, TO and the case number of the last case to print, and BY and the number of cases to advance between printing cases, or any subset of those settings.  If CASES is not specified then all cases are printed.

The FORMAT subcommand can be used to change the output format.  NUMBERED will print case numbers along with each case; UNNUMBERED, the default, causes the case numbers to be omitted.  The WRAP and SINGLE settings are currently not used.  WEIGHT will cause case weights to be printed along with variable values; NOWEIGHT, the default, causes case weights to be omitted from the output.

Case numbers start from 1.  They are counted after all transformations have been considered.

LIST attempts to fit all the values on a single line.  If needed to make them fit, variable names are displayed vertically.  If values cannot fit on a single line, then a multi-line format will be used.

LIST is a procedure.  It causes the data to be read.

MATRIX DATA
===========

     MATRIX DATA
             /VARIABLES=var_list
             /FILE='filename'
             /FORMAT={LIST,FREE} {LOWER,UPPER,FULL} {DIAGONAL,NODIAGONAL}
             /SPLIT={new_var,var_list}
             /FACTORS=var_list
             /CELLS=n_cells
             /N=n
             /CONTENTS={N_VECTOR,N_SCALAR,N_MATRIX,MEAN,STDDEV,COUNT,MSE,
                        DFE,MAT,COV,CORR,PROX}

MATRIX DATA command reads square matrices in one of several textual formats.  MATRIX DATA clears the dictionary and replaces it and reads a data file.

Use VARIABLES to specify the variables that form the rows and columns of the matrices.  You may not specify a variable named VARNAME_.  You should specify VARIABLES first.

Specify the file to read on FILE, either as a file name string or a file handle (see FILE HANDLE).  If FILE is not specified then matrix data must immediately follow MATRIX DATA with a BEGIN
DATA...END DATA construct (see BEGIN DATA).

The FORMAT subcommand specifies how the matrices are formatted.  LIST, the default, indicates that there is one line per row of matrix data; FREE allows single matrix rows to be broken across multiple lines.  This is analogous to the difference between DATA LIST FREE and DATA LIST LIST (see DATA LIST).  LOWER, the default, indicates that the lower triangle of the matrix is given; UPPER indicates the upper triangle; and FULL indicates that the entire matrix is given.  DIAGONAL, the default, indicates that the diagonal is part of the data; NODIAGONAL indicates that it is omitted.  DIAGONAL/NODIAGONAL have no effect when FULL is specified.

The SPLIT subcommand is used to specify SPLIT FILE variables for the input matrices (see SPLIT FILE).  Specify either a single variable not specified on VARIABLES, or one or more variables that are specified on VARIABLES.  In the former case, the SPLIT values are not present in the data and ROWTYPE_ may not be specified on VARIABLES.  In the latter case, the SPLIT values are present in the data.

Specify a list of factor variables on FACTORS.  Factor variables must also be listed on VARIABLES.  Factor variables are used when there are some variables where, for each possible combination of their values, statistics on the matrix variables are included in the data.

If FACTORS is specified and ROWTYPE_ is not specified on VARIABLES, the CELLS subcommand is required.  Specify the number of factor variable combinations that are given.  For instance, if factor variable A has 2 values and factor variable B has 3 values, specify 6.

The N subcommand specifies a population number of observations.  When N is specified, one N record is output for each SPLIT FILE.

Use CONTENTS to specify what sort of information the matrices include. Each possible option is described in more detail below.  When ROWTYPE_ is specified on VARIABLES, CONTENTS is optional; otherwise, if CONTENTS is not specified then /CONTENTS=CORR is assumed.

N

N_VECTOR
     Number of observations as a vector, one value for each variable.

N_SCALAR
     Number of observations as a single value.

N_MATRIX
     Matrix of counts.

MEAN
     Vector of means.

STDDEV
     Vector of standard deviations.

COUNT
     Vector of counts.

MSE
     Vector of mean squared errors.

DFE
     Vector of degrees of freedom.

MAT
     Generic matrix.

COV
     Covariance matrix.

CORR
     Correlation matrix.

PROX
     Proximities matrix.

The exact semantics of the matrices read by MATRIX DATA are complex. Right now MATRIX DATA isn't too useful due to a lack of procedures accepting or producing related data, so these semantics aren't documented.  Later, they'll be described here in detail.

NEW FILE
========

     NEW FILE.

NEW FILE command clears the current active file.

PRINT
=====

     PRINT
             OUTFILE='filename'
             RECORDS=n_lines
             {NOTABLE,TABLE}
             /[line_no] arg...

     arg takes one of the following forms:
             'string' [start-end]
             var_list start-end [type_spec]
             var_list (fortran_spec)
             var_list *

The PRINT transformation writes variable data to an output file. PRINT is executed when a procedure causes the data to be read. Follow PRINT by EXECUTE to print variable data without invoking a procedure (see EXECUTE).

All PRINT subcommands are optional.

The OUTFILE subcommand specifies the file to receive the output.  The file may be a file name as a string or a file handle (see FILE HANDLE).  If OUTFILE is not present then output will be sent to PSPP's output listing file.

The RECORDS subcommand specifies the number of lines to be output.  The number of lines may optionally be surrounded by parentheses.

TABLE will cause the PRINT command to output a table to the listing file that describes what it will print to the output file.  NOTABLE, the default, suppresses this output table.

Introduce the strings and variables to be printed with a slash (/).  Optionally, the slash may be followed by a number indicating which output line will be specified.  In the absence of this line number, the next line number will be specified.  Multiple lines may be specified using multiple slashes with the intended output for a line following its respective slash.

Literal strings may be printed.  Specify the string itself.  Optionally the string may be followed by a column number or range of column numbers, specifying the location on the line for the string to be printed.  Otherwise, the string will be printed at the current position on the line.

Variables to be printed can be specified in the same ways as available for DATA LIST FIXED (see DATA LIST FIXED).  In addition, a variable list may be followed by an asterisk (*), which indicates that the variables should be printed in their dictionary print formats, separated by spaces.  A variable list followed by a slash or the end of command will be interpreted the same way.

If a FORTRAN type specification is used to move backwards on the current line, then text is written at that point on the line, the line will be truncated to that length, although additional text being added will again extend the line to that length.

PRINT EJECT
===========

     PRINT EJECT
             OUTFILE='filename'
             RECORDS=n_lines
             {NOTABLE,TABLE}
             /[line_no] arg...

     arg takes one of the following forms:
             'string' [start-end]
             var_list start-end [type_spec]
             var_list (fortran_spec)
             var_list *

PRINT EJECT writes data to an output file.  Before the data is written, the current page in the listing file is ejected.

See PRINT, for more information on syntax and usage.

PRINT SPACE
===========

     PRINT SPACE OUTFILE='filename' n_lines.

PRINT SPACE prints one or more blank lines to an output file.

The OUTFILE subcommand is optional.  It may be used to direct output to a file specified by file name as a string or file handle (see FILE HANDLE).  If OUTFILE is not specified then output will be directed to the listing file.

n_lines is also optional.  If present, it is an expression (see Expressions) specifying the number of blank lines to be printed.  The expression must evaluate to a nonnegative value.

REREAD
======

     REREAD FILE=handle COLUMN=column.

The REREAD transformation allows the previous input line in a data file already processed by DATA LIST or another input command to be re-read for further processing.

The FILE subcommand, which is optional, is used to specify the file to have its line re-read.  The file must be specified in the form of a file handle (see FILE HANDLE).  If FILE is not specified then the last file specified on DATA LIST will be assumed (last file specified lexically, not in terms of flow-of-control).

By default, the line re-read is re-read in its entirety.  With the COLUMN subcommand, a prefix of the line can be exempted from re-reading.  Specify an expression (see Expressions) evaluating to the first column that should be included in the re-read line.  Columns are numbered from 1 at the left margin.

Issuing REREAD multiple times will not back up in the data file.  Instead, it will re-read the same line multiple times.

REPEATING DATA
==============

     REPEATING DATA
             /STARTS=start-end
             /OCCURS=n_occurs
             /FILE='filename'
             /LENGTH=length
             /CONTINUED[=cont_start-cont_end]
             /ID=id_start-id_end=id_var
             /{TABLE,NOTABLE}
             /DATA=var_spec...

     where each var_spec takes one of the forms
             var_list start-end [type_spec]
             var_list (fortran_spec)

REPEATING DATA parses groups of data repeating in a uniform format, possibly with several groups on a single line.  Each group of data corresponds with one case.  REPEATING DATA may only be used within an INPUT PROGRAM structure (see INPUT PROGRAM). When used with DATA LIST, it can be used to parse groups of cases that share a subset of variables but differ in their other data.

The STARTS subcommand is required.  Specify a range of columns, using literal numbers or numeric variable names.  This range specifies the columns on the first line that are used to contain groups of data.  The ending column is optional.  If it is not specified, then the record width of the input file is used.  For the inline file (see BEGIN DATA) this is 80 columns; for a file with fixed record widths it is the record width; for other files it is 1024 characters by default.

The OCCURS subcommand is required.  It must be a number or the name of a numeric variable.  Its value is the number of groups present in the current record.

The DATA subcommand is required.  It must be the last subcommand specified.  It is used to specify the data present within each repeating group.  Column numbers are specified relative to the beginning of a group at column 1.  Data is specified in the same way as with DATA LIST
FIXED (see DATA LIST FIXED).

All other subcommands are optional.

FILE specifies the file to read, either a file name as a string or a file handle (see FILE HANDLE).  If FILE is not present then the default is the last file handle used on DATA LIST (lexically, not in terms of flow of control).

By default REPEATING DATA will output a table describing how it will parse the input data.  Specifying NOTABLE will disable this behavior; specifying TABLE will explicitly enable it.

The LENGTH subcommand specifies the length in characters of each group. If it is not present then length is inferred from the DATA subcommand. LENGTH can be a number or a variable name.

Normally all the data groups are expected to be present on a single line.  Use the CONTINUED command to indicate that data can be continued onto additional lines.  If data on continuation lines starts at the left margin and continues through the entire field width, no column specifications are necessary on CONTINUED.  Otherwise, specify the possible range of columns in the same way as on STARTS.

When data groups are continued from line to line, it is easy for cases to get out of sync through careless hand editing.  The ID subcommand allows a case identifier to be present on each line of repeating data groups.  REPEATING DATA will check for the same identifier on each line and report mismatches.  Specify the range of columns that the identifier will occupy, followed by an equals sign (=) and the identifier variable name.  The variable must already have been declared with NUMERIC or another command.

REPEATING DATA should be the last command given within an INPUT PROGRAM.  It should not be enclosed within a LOOP structure (see LOOP).  Use DATA LIST before, not after, REPEATING DATA.

WRITE
=====

     WRITE
             OUTFILE='filename'
             RECORDS=n_lines
             {NOTABLE,TABLE}
             /[line_no] arg...

     arg takes one of the following forms:
             'string' [start-end]
             var_list start-end [type_spec]
             var_list (fortran_spec)
             var_list *

WRITE writes text or binary data to an output file.

See PRINT, for more information on syntax and usage.  The main difference between PRINT and WRITE is that WRITE uses write formats by default, where PRINT uses print formats.

The sole additional difference is that if WRITE is used to send output to a binary file, carriage control characters will not be output. See FILE HANDLE, for information on how to declare a file as binary.

System Files and Portable Files
*******************************

The commands in this chapter read, write, and examine system files and portable files.

APPLY DICTIONARY
================

     APPLY DICTIONARY FROM='filename'.

APPLY DICTIONARY applies the variable labels, value labels, and missing values from variables in a system file to corresponding variables in the active file.  In some cases it also updates the weighting variable.

Specify a system file with a file name string or as a file handle (see FILE HANDLE).  The dictionary in the system file will be read, but it will not replace the active file dictionary.  The system file's data will not be read.

Only variables with names that exist in both the active file and the system file are considered.  Variables with the same name but different types (numeric, string) will cause an error message.  Otherwise, the system file variables' attributes will replace those in their matching active file variables, as described below.

If a system file variable has a variable label, then it will replace the active file variable's variable label.  If the system file variable does not have a variable label, then the active file variable's variable label, if any, will be retained.

If the active file variable is numeric or short string, then value labels and missing values, if any, will be copied to the active file variable.  If the system file variable does not have value labels or missing values, then those in the active file variable, if any, will not be disturbed.

Finally, weighting of the active file is updated (see WEIGHT).  If the active file has a weighting variable, and the system file does not, or if the weighting variable in the system file does not exist in the active file, then the active file weighting variable, if any, is retained.  Otherwise, the weighting variable in the system file becomes the active file weighting variable.

APPLY DICTIONARY takes effect immediately.  It does not read the active file.  The system file is not modified.

EXPORT
======

     EXPORT
             /OUTFILE='filename'
             /DROP=var_list
             /KEEP=var_list
             /RENAME=(src_names=target_names)...

The EXPORT procedure writes the active file dictionary and data to a specified portable file.

The OUTFILE subcommand, which is the only required subcommand, specifies the portable file to be written as a file name string or a file handle (see FILE HANDLE).

DROP, KEEP, and RENAME follow the same format as the SAVE procedure (see SAVE).

EXPORT is a procedure.  It causes the active file to be read.

GET
===

     GET
             /FILE='filename'
             /DROP=var_list
             /KEEP=var_list
             /RENAME=(src_names=target_names)...

GET clears the current dictionary and active file and replaces them with the dictionary and data from a specified system file.

The FILE subcommand is the only required subcommand.  Specify the system file to be read as a string file name or a file handle (see FILE HANDLE).

By default, all the variables in a system file are read.  The DROP subcommand can be used to specify a list of variables that are not to be read.  By contrast, the KEEP subcommand can be used to specify variable that are to be read, with all other variables not read.

Normally variables in a system file retain the names that they were saved under.  Use the RENAME subcommand to change these names.  Specify, within parentheses, a list of variable names followed by an equals sign (=) and the names that they should be renamed to.  Multiple parenthesized groups of variable names can be included on a single RENAME subcommand.  Variables' names may be swapped using a RENAME subcommand of the form /RENAME=(A B=B A).

Alternate syntax for the RENAME subcommand allows the parentheses to be eliminated.  When this is done, only a single variable may be renamed at once.  For instance, /RENAME=A=B.  This alternate syntax is deprecated.

DROP, KEEP, and RENAME are performed in left-to-right order.  They each may be present any number of times.  GET never modifies a system file on disk.  Only the active file read from the system file is affected by these subcommands.

GET does not cause the data to be read, only the dictionary.  The data is read later, when a procedure is executed.

IMPORT
======

     IMPORT
             /FILE='filename'
             /TYPE={COMM,TAPE}
             /DROP=var_list
             /KEEP=var_list
             /RENAME=(src_names=target_names)...

The IMPORT transformation clears the active file dictionary and data and replaces them with a dictionary and data from a portable file on disk.

The FILE subcommand, which is the only required subcommand, specifies the portable file to be read as a file name string or a file handle (see FILE HANDLE).

The TYPE subcommand is currently not used.

DROP, KEEP, and RENAME follow the syntax used by GET (see GET).

IMPORT does not cause the data to be read, only the dictionary.  The data is read later, when a procedure is executed.

MATCH FILES
===========

     MATCH FILES
             /BY var_list
             /{FILE,TABLE}={*,'filename'}
             /DROP=var_list
             /KEEP=var_list
             /RENAME=(src_names=target_names)...
             /IN=var_name
             /FIRST=var_name
             /LAST=var_name
             /MAP

MATCH FILES merges one or more system files, optionally including the active file.  Records with the same values for BY variables are combined into a single record.  Records with different values are output in order.  Thus, multiple sorted system files are combined into a single sorted system file based on the value of the BY variables.

The BY subcommand specifies a list of variables that are used to match records from each of the system files.  Variables specified must exist in all the files specified on FILE and TABLE.  BY should usually be specified.  If TABLE is used then BY is required.

Specify FILE with a system file as a file name string or file handle (see FILE HANDLE), or with an asterisk (*) to indicate the current active file.  The files specified on FILE are merged together based on the BY variables, or combined case-by-case if BY is not specified.  Normally at least two FILE subcommands should be specified.

Specify TABLE with a system file to use it as a table lookup file.  Records in table lookup files are not used up after they've been used once.  This means that data in table lookup files can correspond to any number of records in FILE files.  Table lookup files correspond to lookup tables in traditional relational database systems. It is incorrect to have records with duplicate BY values in table lookup files.

Any number of FILE and TABLE subcommands may be specified.  Each instance of FILE or TABLE can be followed by DROP, KEEP, and/or RENAME subcommands.  These take the same form as the corresponding subcommands of GET (see GET), and perform the same functions.

Variables belonging to files that are not present for the current case are set to the system-missing value for numeric variables or spaces for string variables.

IN, FIRST, LAST, and MAP are currently not used.

SAVE
====

     SAVE
             /OUTFILE='filename'
             /{COMPRESSED,UNCOMPRESSED}
             /DROP=var_list
             /KEEP=var_list
             /RENAME=(src_names=target_names)...

The SAVE procedure causes the dictionary and data in the active file to be written to a system file.

FILE is the only required subcommand.  Specify the system file to be written as a string file name or a file handle (see FILE HANDLE).

The COMPRESS and UNCOMPRESS subcommand determine whether the saved system file is compressed.  By default, system files are compressed. This default can be changed with the SET command (see SET).

By default, all the variables in the active file dictionary are written to the system file.  The DROP subcommand can be used to specify a list of variables not to be written.  In contrast, KEEP specifies variables to be written, with all variables not specified not written.

Normally variables are saved to a system file under the same names they have in the active file.  Use the RENAME subcommand to change these names. Specify, within parentheses, a list of variable names followed by an equals sign (=) and the names that they should be renamed to. Multiple parenthesized groups of variable names can be included on a single RENAME subcommand.  Variables' names may be swapped using a RENAME subcommand of the form /RENAME=(A B=B A).

Alternate syntax for the RENAME subcommand allows the parentheses to be eliminated.  When this is done, only a single variable may be renamed at once.  For instance, /RENAME=A=B.  This alternate syntax is deprecated.

DROP, KEEP, and RENAME are performed in left-to-right order.  They each may be present any number of times.  SAVE never modifies the active file.  DROP, KEEP, and RENAME only affect the system file written to disk.

SAVE causes the data to be read.  It is a procedure.

SYSFILE INFO
============

     SYSFILE INFO FILE='filename'.

SYSFILE INFO reads the dictionary in a system file and displays the information in its dictionary.

Specify a file name or file handle.  SYSFILE INFO reads that file as a system file and displays information on its dictionary.

SYSFILE INFO does not affect the current active file.

XSAVE
=====

     XSAVE
             /FILE='filename'
             /{COMPRESSED,UNCOMPRESSED}
             /DROP=var_list
             /KEEP=var_list
             /RENAME=(src_names=target_names)...

The XSAVE transformation writes the active file dictionary and data to a system file stored on disk.

XSAVE is a transformation, not a procedure.  It is executed when the data is read by a procedure or procedure-like command.  In all other respects, XSAVE is identical to SAVE.  See SAVE, for more information on syntax and usage.

Manipulating variables
**********************

The variables in the active file dictionary are important.  There are several utility functions for examining and adjusting them.

ADD VALUE LABELS
================

     ADD VALUE LABELS
             /var_list value 'label' [value 'label']...

ADD VALUE LABELS has the same syntax and purpose as VALUE
LABELS (see VALUE LABELS), but it does not clear value labels from the variables before adding the ones specified.

DISPLAY
=======

     DISPLAY {NAMES,INDEX,LABELS,VARIABLES,DICTIONARY,SCRATCH}
             [SORTED] [var_list]

DISPLAY displays requested information on variables.  Variables can optionally be sorted alphabetically.  The entire dictionary or just specified variables can be described.

One of the following keywords can be present:

NAMES
     The variables' names are displayed.

INDEX
     The variables' names are displayed along with a value describing their position within the active file dictionary.

LABELS
     Variable names, positions, and variable labels are displayed.

VARIABLES
     Variable names, positions, print and write formats, and missing values are displayed.

DICTIONARY
     Variable names, positions, print and write formats, missing values, variable labels, and value labels are displayed.

SCRATCH
     Varible names are displayed, for scratch variables only (see Scratch Variables).

If SORTED is specified, then the variables are displayed in ascending order based on their names; otherwise, they are displayed in the order that they occur in the active file dictionary.

DISPLAY VECTORS
===============

     DISPLAY VECTORS.

DISPLAY VECTORS lists all the currently declared vectors.

FORMATS
=======

     FORMATS var_list (fmt_spec).

FORMATS set both print and write formats for the specified variables to the specified format specification.  See Input/Output Formats.

Specify a list of variables followed by a format specification in parentheses.  The print and write formats of the specified variables will be changed.

Additional lists of variables and formats may be included if they are delimited by a slash (/).

FORMATS takes effect immediately.  It is not affected by conditional and looping structures such as DO IF or LOOP.

LEAVE
=====

     LEAVE var_list.

LEAVE prevents the specified variables from being reinitialized whenever a new case is processed.

Normally, when a data file is processed, every variable in the active file is initialized to the system-missing value or spaces at the beginning of processing for each case.  When a variable has been specified on LEAVE, this is not the case.  Instead, that variable is initialized to 0 (not system-missing) or spaces for the first case. After that, it retains its value between cases.

This becomes useful for counters.  For instance, in the example below the variable SUM maintains a running total of the values in the ITEM variable.

     DATA LIST /ITEM 1-3.
     COMPUTE SUM=SUM+ITEM.
     PRINT /ITEM SUM.
     LEAVE SUM
     BEGIN DATA.
     123
     404
     555
     999
     END DATA.

Partial output from this example:

     123   123.00
     404   527.00
     555  1082.00
     999  2081.00

It is best to use LEAVE command immediately before invoking a procedure command, because the left status of variables is reset by certain transformations---for instance, COMPUTE and IF. Left status is also reset by all procedure invocations.

MISSING VALUES
==============

     MISSING VALUES var_list (missing_values).

     missing_values takes one of the following forms:
             num1
             num1, num2
             num1, num2, num3
             num1 THRU num2
             num1 THRU num2, num3
             string1
             string1, string2
             string1, string2, string3
     As part of a range, LO or LOWEST may take the place of num1;
     HI or HIGHEST may take the place of num2.

MISSING VALUES sets user-missing values for numeric and short string variables.  Long string variables may not have missing values.

Specify a list of variables, followed by a list of their user-missing values in parentheses.  Up to three discrete values may be given, or, for numeric variables only, a range of values optionally accompanied by a single discrete value.  Ranges may be open-ended on one end, indicated through the use of the keyword LO or LOWEST or HI or HIGHEST.

The MISSING VALUES command takes effect immediately.  It is not affected by conditional and looping constructs such as DO IF or LOOP.

MODIFY VARS
===========

     MODIFY VARS
             /REORDER={FORWARD,BACKWARD} {POSITIONAL,ALPHA} (var_list)...
             /RENAME=(old_names=new_names)...
             /{DROP,KEEP}=var_list
             /MAP

MODIFY VARS reorders, renames, and deletes variables in the active file.

At least one subcommand must be specified, and no subcommand may be specified more than once.  DROP and KEEP may not both be specified.

The REORDER subcommand changes the order of variables in the active file.  Specify one or more lists of variable names in parentheses.  By default, each list of variables is rearranged into the specified order. To put the variables into the reverse of the specified order, put keyword BACKWARD before the parentheses.  To put them into alphabetical order in the dictionary, specify keyword ALPHA before the parentheses. BACKWARD and ALPHA may also be combined.

To rename variables in the active file, specify RENAME, an equals sign (=), and lists of the old variable names and new variable names separated by another equals sign within parentheses.  There must be the same number of old and new variable names.  Each old variable is renamed to the corresponding new variable name.  Multiple parenthesized groups of variables may be specified.

The DROP subcommand deletes a specified list of variables from the active file.

The KEEP subcommand keeps the specified list of variables in the active file.  Any unlisted variables are deleted from the active file.

MAP is currently ignored.

If either DROP or KEEP is specified, the data is read; otherwise it is not.

NUMERIC
=======

     NUMERIC /var_list [(fmt_spec)].

NUMERIC explicitly declares new numeric variables, optionally setting their output formats.

Specify a slash (/), followed by the names of the new numeric variables.  If you wish to set their output formats, follow their names by an output format specification in parentheses (see Input/Output Formats); otherwise, the default is F8.2.

Variables created with NUMERIC are initialized to the system-missing value.

PRINT FORMATS
=============

     PRINT FORMATS var_list (fmt_spec).

PRINT FORMATS sets the print formats for the specified variables to the specified format specification.

Its syntax is identical to that of FORMATS (see FORMATS), but PRINT FORMATS sets only print formats, not write formats.

RENAME VARIABLES
================

     RENAME VARIABLES (old_names=new_names)... .

RENAME VARIABLES changes the names of variables in the active file.  Specify lists of the old variable names and new variable names, separated by an equals sign (=), within parentheses.  There must be the same number of old and new variable names.  Each old variable is renamed to the corresponding new variable name.  Multiple parenthesized groups of variables may be specified.

RENAME VARIABLES takes effect immediately.  It does not cause the data to be read.

VALUE LABELS
============

     VALUE LABELS
             /var_list value 'label' [value 'label']...

VALUE LABELS allows values of numeric and short string variables to be associated with labels.  In this way, a short value can stand for a long value.

To set up value labels for a set of variables, specify the variable names after a slash (/), followed by a list of values and their associated labels, separated by spaces.  Long string variables may not be specified.

Before VALUE LABELS is executed, any existing value labels are cleared from the variables specified.  Use ADD VALUE LABELS (see ADD VALUE LABELS) to add value labels without clearing those already present.

STRING
======

     STRING /var_list (fmt_spec).

STRING creates new string variables for use in transformations.

Specify a slash (/), followed by the names of the string variables to create and the desired output format specification in parentheses (see Input/Output Formats).  Variable widths are implicitly derived from the specified output formats.

Created variables are initialized to spaces.

VARIABLE LABELS
===============

     VARIABLE LABELS
             /var_list 'var_label'.

VARIABLE LABELS associates explanatory names with variables.  This name, called a variable label, is displayed by statistical procedures.

To assign a variable label to a group of variables, specify a slash (/), followed by the list of variable names and the variable label as a string.

VECTOR
======

     Two possible syntaxes:
             VECTOR vec_name=var_list.
             VECTOR vec_name_list(count).

VECTOR allows a group of variables to be accessed as if they were consecutive members of an array with a vector(index) notation.

To make a vector out of a set of existing variables, specify a name for the vector followed by an equals sign (=) and the variables that belong in the vector.

To make a vector and create variables at the same time, specify one or more vector names followed by a count in parentheses.  This will cause variables named VEC1 through VECCOUNT to be created as numeric variables with print and write format F8.2. Variable names including numeric suffixes may not exceed 8 characters in length, and none of the variables may exist prior to VECTOR.

All the variables in a vector must be the same type.

Vectors created with VECTOR disappear after any procedure or procedure-like command is executed.  The variables contained in the vectors remain, unless they are scratch variables (see Scratch Variables).

Variables within a vector may be references in expressions using vector(index) syntax.

WRITE FORMATS
=============

     WRITE FORMATS var_list (fmt_spec).

WRITE FORMATS sets the write formats for the specified variables to the specified format specification.  Its syntax is identical to that of FORMATS (see FORMATS), but WRITE FORMATS sets only write formats, not print formats.

Data transformations
********************

The PSPP procedures examined in this chapter manipulate data and prepare the active file for later analyses.  They do not produce output, as a rule.

AGGREGATE
=========

     AGGREGATE
             /BREAK=var_list
             /PRESORTED
             /OUTFILE={*,'filename'}
             /DOCUMENT
             /MISSING=COLUMNWISE
             /dest_vars=agr_func(src_vars, args...)...

AGGREGATE summarizes groups of cases into single cases. Cases are divided into groups that have the same values for one or more variables called break variables.  Several functions are available for summarizing case contents.

At least one break variable must be specified on BREAK, the only required subcommand.  The values of these variables are used to divide the active file into groups to be summarized.  In addition, at least one DEST_VAR must be specified.

By default, the active file is sorted based on the break variables before aggregation takes place.  If the active file is already sorted or otherwise grouped in terms of the break variables, specify PRESORTED to save time.

The OUTFILE subcommand specifies a system file by file name string or file handle (see FILE HANDLE).  The aggregated cases are written to this file.  If OUTFILE is not specified, or if * is specified, then the aggregated cases replace the active file.

Specify DOCUMENT to copy the documents from the active file into the aggregate file (see DOCUMENT).  Otherwise, the aggregate file will not contain any documents, even if the aggregate file replaces the active file.

One or more sets of aggregation variables must be specified.  Each set comprises a list of aggregation variables, an equals sign (=), the name of an aggregation function (see the list below), and a list of source variables in parentheses.  Some aggregation functions expect additional arguments following the source variable names.

Each set must have exactly as many source variables as aggregation variables.  Each aggregation variable receives the results of applying the specified aggregation function to the corresponding source variable.  Most aggregation functions may be applied to numeric and short and long string variables.  Others, marked below, are restricted to numeric values.

The available aggregation functions are as follows:

SUM(var_name)
     Sum.  Limited to numeric values.

MEAN(var_name)
     Arithmetic mean.  Limited to numeric values.

SD(var_name)
     Standard deviation of the mean.  Limited to numeric values.

MAX(var_name)
     Maximum value.

MIN(var_name)
     Minimum value.

FGT(var_name, value)
PGT(var_name, value)
     Fraction between 0 and 1, or percentage between 0 and 100, respectively, of values greater than the specified constant.

FLT(var_name, value)
PLT(var_name, value)
     Fraction or percentage, respectively, of values less than the specified constant.

FIN(var_name, low, high)
PIN(var_name, low, high)
     Fraction or percentage, respectively, of values within the specified inclusive range of constants.

FOUT(var_name, low, high)
POUT(var_name, low, high)
     Fraction or percentage, respectively, of values strictly outside the specified range of constants.

N(var_name)
     Number of non-missing values.

N
     Number of cases aggregated to form this group.  Don't supply a source variable for this aggregation function.

NU(var_name)
     Number of non-missing values.  Each case is considered to have a weight of 1, regardless of the current weighting variable (see WEIGHT).

NU
     Number of cases aggregated to form this group.  Each case is considered to have a weight of 1, regardless of the current weighting variable.

NMISS(var_name)
     Number of missing values.

NUMISS(var_name)
     Number of missing values.  Each case is considered to have a weight of 1, regardless of the current weighting variable.

FIRST(var_name)
     First value in this group.

LAST(var_name)
     Last value in this group.

Aggregation functions compare string values in terms of internal character codes.  On most modern computers, this is a form of ASCII.

The aggregation functions listed above exclude all user-missing values from calculations.  To include user-missing values, insert a period (.) between the function name and left parenthesis (e.g.~SUM.).

Normally, only a single case (for SD and SD., two cases) need be non-missing in each group for the aggregate variable to be non-missing.  Specifying /MISSING=COLUMNWISE inverts this behavior, so that the aggregate variable becomes missing if any aggregated value is missing.

AGGREGATE both ignores and cancels the current SPLIT FILE settings (see SPLIT FILE).

AUTORECODE
==========

     AUTORECODE VARIABLES=src_vars INTO dest_vars
             /DESCENDING
             /PRINT

The AUTORECODE procedure considers the N values that a variable takes on and maps them onto values 1...N on a new numeric variable.

Subcommand VARIABLES is the only required subcommand and must come first.  Specify VARIABLES, an equals sign (=), a list of source variables, INTO, and a list of target variables.  There must the same number of source and target variables.  The target variables must not already exist.

By default, increasing values of a source variable (for a string, this is based on character code comparisons) are recoded to increasing values of its target variable.  To cause increasing values of a source variable to be recoded to decreasing values of its target variable (N down to 1), specify DESCENDING.

PRINT is currently ignored.

AUTORECODE is a procedure.  It causes the data to be read.

COMPUTE
=======

     COMPUTE variable = expression.
       or
     COMPUTE vector(index) = expression.

COMPUTE assigns the value of an expression to a target variable.  For each case, the expression is evaluated and its value assigned to the target variable.  Numeric and short and long string variables may be assigned.  When a string expression's width differs from the target variable's width, the string result of the expression is truncated or padded with spaces on the right as necessary.  The expression and variable types must match.

For numeric variables only, the target variable need not already exist.  Numeric variables created by COMPUTE are assigned an F8.2 output format.  String variables must be declared before they can be used as targets for COMPUTE.

The target variable may be specified as an element of a vector (see VECTOR).  In this case, a vector index expression must be specified in parentheses following the vector name.  The index expression must evaluate to a numeric value that, after rounding down to the nearest integer, is a valid index for the named vector.

Using COMPUTE to assign to a variable specified on LEAVE (see LEAVE) resets the variable's left state.  Therefore, LEAVE should be specified following COMPUTE, not before.

COMPUTE is a transformation.  It does not cause the active file to be read.

COUNT
=====

     COUNT var_name = var... (value...).

     Each value takes one of the following forms:
             number
             string
             num1 THRU num2
             MISSING
             SYSMIS
     In addition, num1 and num2 can be LO or LOWEST, or HI or HIGHEST,
     respectively.

COUNT creates or replaces a numeric target variable that counts the occurrence of a criterion value or set of values over one or more test variables for each case.

The target variable values are always nonnegative integers.  They are never missing.  The target variable is assigned an F8.2 output format. See Input/Output Formats.  Any variables, including long and short string variables, may be test variables.

User-missing values of test variables are treated just like any other values.  They are not treated as system-missing values. User-missing values that are criterion values or inside ranges of criterion values are counted as any other values.  However (for numeric variables), keyword MISSING may be used to refer to all system- and user-missing values.

COUNT target variables are assigned values in the order specified.  In the command COUNT A=A B(1) /B=A B(2)., the following actions occur:

  - The number of occurrences of 1 between A and B is counted.

  - A is assigned this value.

  - The number of occurrences of 1 between B and the new value of A is counted.

  - B is assigned this value.

Despite this ordering, all COUNT criterion variables must exist before the procedure is executed---they may not be created as target variables earlier in the command!  Break such a command into two separate commands.

The examples below may help to clarify.

 A. Assuming Q0, Q2, ..., Q9 are numeric variables, the following commands:

      1. Count the number of times the value 1 occurs through these variables for each case and assigns the count to variable QCOUNT.

      2. Print out the total number of times the value 1 occurs throughout all cases using DESCRIPTIVES.  See DESCRIPTIVES, for details.

          COUNT QCOUNT=Q0 TO Q9(1).
          DESCRIPTIVES QCOUNT /STATISTICS=SUM.

 B. Given these same variables, the following commands:

      1. Count the number of valid values of these variables for each case and assigns the count to variable QVALID.

      2. Multiplies each value of QVALID by 10 to obtain a percentage of valid values, using COMPUTE.  See COMPUTE, for details.

      3. Print out the percentage of valid values across all cases, using DESCRIPTIVES.  See DESCRIPTIVES, for details.

          COUNT QVALID=Q0 TO Q9 (LO THRU HI).
          COMPUTE QVALID=QVALID*10.
          DESCRIPTIVES QVALID /STATISTICS=MEAN.

FLIP
====

     FLIP /VARIABLES=var_list /NEWNAMES=var_name.

FLIP transposes rows and columns in the active file.  It causes cases to be swapped with variables, and vice versa.

All variables in the transposed active file are numeric.  String variables take on the system-missing value in the transposed file.

No subcommands are required.  The VARIABLES subcommand specifies variables that will be transformed into cases.  Variables not specified are discarded.  By default, all variables are selected for transposition.

The variables specified by NEWNAMES, which must be a string variable, is used to give names to the variables created by FLIP.  If NEWNAMES is not specified then the default is a variable named CASE_LBL, if it exists. If it does not then the variables created by FLIP are named VAR000 through VAR999, then VAR1000, VAR1001, and so on.

When a NEWNAMES variable is available, the names must be canonicalized before becoming variable names.  Invalid characters are replaced by letter V in the first position, or by _ in subsequent positions.  If the name thus generated is not unique, then numeric extensions are added, starting with 1, until a unique name is found or there are no remaining possibilities.  If the latter occurs then the FLIP operation aborts.

The resultant dictionary contains a CASE_LBL variable, which stores the names of the variables in the dictionary before the transposition.  If the active file is subsequently transposed using FLIP, this variable can be used to recreate the original variable names.

IF
==

     IF condition variable=expression.
       or
     IF condition vector(index)=expression.

The IF transformation conditionally assigns the value of a target expression to a target variable, based on the truth of a test expression.

Specify a boolean-valued expression (see Expressions) to be tested following the IF keyword.  This expression is evaluated for each case. If the value is true, then the value of the expression is computed and assigned to the specified variable.  If the value is false or missing, nothing is done.  Numeric and short and long string variables may be assigned.  When a string expression's width differs from the target variable's width, the string result of the expression is truncated or padded with spaces on the right as necessary.  The expression and variable types must match.

The target variable may be specified as an element of a vector (see VECTOR).  In this case, a vector index expression must be specified in parentheses following the vector name.  The index expression must evaluate to a numeric value that, after rounding down to the nearest integer, is a valid index for the named vector.

Using IF to assign to a variable specified on LEAVE (see LEAVE) resets the variable's left state.  Therefore, LEAVE should be specified following IF, not before.

RECODE
======

     RECODE var_list (src_value...=dest_value)... [INTO var_list].

     src_value may take the following forms:
             number
             string
             num1 THRU num2
             MISSING
             SYSMIS
             ELSE
     Open-ended ranges may be specified using LO or LOWEST for num1
     or HI or HIGHEST for num2.

     dest_value may take the following forms:
             num
             string
             SYSMIS
             COPY

RECODE translates data from one range of values to another, via flexible user-specified mappings.  Data may be remapped in-place or copied to new variables.  Numeric, short string, and long string data can be recoded.

Specify the list of source variables, followed by one or more mapping specifications each enclosed in parentheses.  If the data is to be copied to new variables, specify INTO, then the list of target variables.  String target variables must already have been declared using STRING or another transformation, but numeric target variables can be created on the fly.  There must be exactly as many target variables as source variables.  Each source variable is remapped into its corresponding target variable.

When INTO is not used, the input and output variables must be of the same type.  Otherwise, string values can be recoded into numeric values, and vice versa.  When this is done and there is no mapping for a particular value, either a value consisting of all spaces or the system-missing value is assigned, depending on variable type.

Mappings are considered from left to right.  The first src_value that matches the value of the source variable causes the target variable to receive the value indicated by the dest_value.  Literal number, string, and range src_value's should be self-explanatory.  MISSING as a src_value matches any user- or system-missing value.  SYSMIS matches the system missing value only.  ELSE is a catch-all that matches anything. It should be the last src_value specified.

Numeric and string dest_value's should also be self-explanatory.  COPY causes the input values to be copied to the output.  This is only value if the source and target variables are of the same type.  SYSMIS indicates the system-missing value.

If the source variables are strings and the target variables are numeric, then there is one additional mapping available: (CONVERT), which must be the last specified mapping.  CONVERT causes a number specified as a string to be converted to a numeric value.  If the string cannot be parsed as a number, then the system-missing value is assigned.

Multiple recodings can be specified on a single RECODE invocation. Introduce additional recodings with a slash (/) to separate them from the previous recodings.

SORT CASES
==========

     SORT CASES BY var_list.

SORT CASES sorts the active file by the values of one or more variables.

Specify BY and a list of variables to sort by.  By default, variables are sorted in ascending order.  To override sort order, specify (D) or (DOWN) after a list of variables to get descending order, or (A) or (UP) for ascending order.  These apply to the entire list of variables preceding them.

SORT CASES is a procedure.  It causes the data to be read.

SORT CASES attempts to sort the entire active file in main memory. If main memory is exhausted, it falls back to a merge sort algorithm that involves writing and reading numerous temporary files.  Environment variables determine the temporary files' location.  The first of SPSSTMPDIR, SPSSXTMPDIR, or TMPDIR that is set determines the location. Otherwise, if the compiler environment defined P_tmpdir, that is used. Otherwise, under Unix-like OSes /tmp is used; under MS-DOS, the first of TEMP, TMP, or root on the current drive is used; under other OSes, the current directory.

Selecting data for analysis
***************************

This chapter documents PSPP commands that temporarily or permanently select data records from the active file for analysis.

FILTER
======

     FILTER BY var_name.
     FILTER OFF.

FILTER allows a boolean-valued variable to be used to select cases from the data stream for processing.

To set up filtering, specify BY and a variable name.  Keyword BY is optional but recommended.  Cases which have a zero or system- or user-missing value are excluded from analysis, but not deleted from the data stream.  Cases with other values are analyzed.

FILTER OFF turns off case filtering.

Filtering takes place immediately before cases pass to a procedure for analysis.  Only one filter variable may be active at a time.  Normally, case filtering continues until it is explicitly turned off with FILTER
OFF.  However, if FILTER is placed after TEMPORARY, filtering stops after execution of the next procedure or procedure-like command.

N OF CASES
==========

     N [OF CASES] num_of_cases [ESTIMATED].

Sometimes you may want to disregard cases of your input.  N can do this.  N 100 tells PSPP to disregard all cases after the first 100.

If the value specified for N is greater than the number of cases read in, the value is ignored.

N does not discard cases or prevent them from being read.  It just causes cases beyond the last one specified to be ignored by data analysis commands.

A later N command can increase or decrease the number of cases selected.  (To select all the cases without knowing how many there are, specify a very high number: 100000 or whatever you think is large enough.)

Transformation procedures performed after N is executed do cause cases to be discarded.

SAMPLE, PROCESS IF, and SELECT IF have precedence over N---the same results are obtained by both of the following fragments, given the same random number seeds:

     ...set up, read in data...
     N 100.
     SAMPLE .5.
     ...analyze data...

     ...set up, read in data...
     SAMPLE .5.
     N 100.
     ...analyze data...

Both fragments above first randomly sample approximately half of the cases, then select the first 100 of those sampled.

N with the ESTIMATED keyword gives an estimated number of cases before DATA LIST or another command to read in data.  ESTIMATED never limits the number of cases processed by procedures.  PSPP currently does not make use of case count estimates.

PROCESS IF
==========

     PROCESS IF expression.

PROCESS IF temporarily eliminates cases from the data stream.  Its effects are active only through the execution of the next procedure or procedure-like command.

Specify a boolean expression (see Expressions).  If the value of the expression is true for a particular case, the case will be analyzed.  If the expression has a false or missing value, then the case will be deleted from the data stream for this procedure only.

Regardless of its placement relative to other commands, PROCESS IF always takes effect immediately before data passes to the procedure. Only one PROCESS IF command may be in effect at any given time.

The effects of PROCESS IF are similar, but not identical, to the effects of executing TEMPORARY, then SELECT IF (see SELECT IF).

PROCESS IF is deprecated.  It is included for compatibility with old command files.  New syntax files should use SELECT IF or FILTER instead.

SAMPLE
======

     SAMPLE num1 [FROM num2].

SAMPLE is used to randomly sample a proportion of the cases in the active file.  SAMPLE is temporary, affecting only the next procedure, unless that is a data transformation, such as SELECT IF or RECODE.

The proportion to sample can be expressed as a single number between 0 and 1.  If k is the number specified, and N is the number of currently-selected cases in the active file, then after SAMPLE K., approximately k*N cases will be selected.

The proportion to sample can also be specified in the style SAMPLE M FROM N.  With this style, cases are selected as follows:

 1. If N is equal to the number of currently-selected cases in the active file, exactly M cases will be selected.

 2. If N is greater than the number of currently-selected cases in the active file, an equivalent proportion of cases will be selected.

 3. If N is less than the number of currently-selected cases in the active, exactly M cases will be selected from the first N cases in the active file.

SAMPLE, SELECT IF, and PROCESS IF are performed in the order specified by the syntax file.

SAMPLE is ignored before SORT CASES.

SAMPLE is always performed before N OF CASES, regardless of ordering in the syntax file.  See N OF CASES.

The same values for SAMPLE may result in different samples.  To obtain the same sample, use the SET command to set the random number seed to the same value before each SAMPLE.  Different samples may still result when the file is processed on systems with differing endianness or floating-point formats.  By default, the random number seed is based on the system time.

SELECT IF
=========

     SELECT IF expression.

SELECT IF selects cases for analysis based on the value of a boolean expression.  Cases not selected are permanently eliminated from the active file, unless TEMPORARY is in effect (see TEMPORARY).

Specify a boolean expression (see Expressions).  If the value of the expression is true for a particular case, the case will be analyzed.  If the expression has a false or missing value, then the case will be deleted from the data stream.

Place SELECT IF as early in the command file as possible.  Cases that are deleted early can be processed more efficiently in time and space.

SPLIT FILE
==========

     Two possible syntaxes:
             SPLIT FILE BY var_list.
             SPLIT FILE OFF.

SPLIT FILE allows multiple sets of data present in one data file to be analyzed separately using single statistical procedure commands.

Specify a list of variable names to analyze multiple sets of data separately.  Groups of cases having the same values for these variables are analyzed by statistical procedure commands as one group. An independent analysis is carried out for each group of cases, and the variable values for the group are printed along with the analysis.

Specify OFF to disable SPLIT FILE and resume analysis of the entire active file as a single group of data.

TEMPORARY
=========

     TEMPORARY.

TEMPORARY is used to make the effects of transformations following its execution temporary.  These transformations will affect only the execution of the next procedure or procedure-like command.  Their effects will not be saved to the active file.

The only specification is the command name.

TEMPORARY may not appear within a DO IF or LOOP construct.  It may appear only once between procedures and procedure-like commands.

An example may help to clarify:

     DATA LIST /X 1-2.
     BEGIN DATA.
      2
      4
     10
     15
     20
     24
     END DATA.
     COMPUTE X=X/2.
     TEMPORARY.
     COMPUTE X=X+3.
     DESCRIPTIVES X.
     DESCRIPTIVES X.

The data read by the first DESCRIPTIVES are 4, 5, 8, 10.5, 13, 15.  The data read by the first DESCRIPTIVES are 1, 2, 5, 7.5, 10, 12.

WEIGHT
======

     WEIGHT BY var_name.
     WEIGHT OFF.

WEIGHT assigns cases varying weights, changing the frequency distribution of the active file.  Execution of WEIGHT is delayed until data have been read.

If a variable name is specified, WEIGHT causes the values of that variable to be used as weighting factors for subsequent statistical procedures.  Use of keyword BY is optional but recommended.  Weighting variables must be numeric.  Scratch variables may not be used for weighting (see Scratch Variables).

When OFF is specified, subsequent statistical procedures will weight all cases equally.

A positive integer weighting factor W on a case will yield the same statistical output as would replicating the case W times. A weighting factor of 0 is treated for statistical purposes as if the case did not exist in the input.  Weighting values need not be integers, but negative and system-missing values for the weighting variable are interpreted as weighting factors of 0.  User-missing values are not treated specially.

WEIGHT does not cause cases in the active file to be replicated in memory.

Conditional and Looping Constructs
**********************************

This chapter documents PSPP commands used for conditional execution, looping, and flow of control.

BREAK
=====

     BREAK.

BREAK terminates execution of the innermost currently executing LOOP construct.

BREAK is allowed only inside LOOP...END LOOP. See LOOP, for more details.

DO IF
=====

     DO IF condition.
             ...
     [ELSE IF condition.
             ...
     ]...
     [ELSE.
             ...]
     END IF.

DO IF allows one of several sets of transformations to be executed, depending on user-specified conditions.

If the specified boolean expression evaluates as true, then the block of code following DO IF is executed.  If it evaluates as missing, then none of the code blocks is executed.  If it is false, then the boolean expression on the first ELSE IF, if present, is tested in turn, with the same rules applied.  If all expressions evaluate to false, then the ELSE code block is executed, if it is present.

DO REPEAT
=========

     DO REPEAT repvar_name=expansion....
             ...
     END REPEAT [PRINT].

     expansion takes one of the following forms:
             var_list
             num_or_range...
             'string'...

     num_or_range takes one of the following forms:
             number
             num1 TO num2

DO REPEAT repeats a block of code, textually substituting different variables, numbers, or strings into the block with each repetition.

Specify a repeat variable name followed by an equals sign (=) and the list of replacements.  Replacements can be a list of variables (which may be existing variables or new variables or a combination thereof), of numbers, or of strings.  When new variable names are specified, DO REPEAT creates them as numeric variables.  When numbers are specified, runs of integers may be indicated with TO notation, for instance 1 TO 5 and 1 2 3 4 5 would be equivalent.  There is no equivalent notation for string values.

Multiple repeat variables can be specified.  When this is done, each variable must have the same number of replacements.

The code within DO REPEAT is repeated as many times as there are replacements for each variable.  The first time, the first value for each repeat variable is substituted; the second time, the second value for each repeat variable is substituted; and so on.

Repeat variable substitutions work like macros.  They take place anywhere in a line that the repeat variable name occurs as a token, including command and subcommand names.  For this reason it is not a good idea to select words commonly used in command and subcommand names as repeat variable identifiers.

If PRINT is specified on END REPEAT, the commands after substitutions are made are printed to the listing file, prefixed by a plus sign (+).

LOOP
====

     LOOP [index_var=start TO end [BY incr]] [IF condition].
             ...
     END LOOP [IF condition].

LOOP iterates a group of commands.  A number of termination options are offered.

Specify index_var to make that variable count from one value to another by a particular increment.  index_var must be a pre-existing numeric variable.  start, end, and incr are numeric expressions (see Expressions.)

During the first iteration, index_var is set to the value of start. During each successive iteration, index_var is increased by the value of incr.  If end > start, then the loop terminates when index_var > end; otherwise it terminates when index_var < end.  If incr is not specified then it defaults to +1 or -1 as appropriate.

If end > start and incr < 0, or if end < start and incr > 0, then the loop is never executed.  index_var is nevertheless set to the value of start.

Modifying index_var within the loop is allowed, but it has no effect on the value of index_var in the next iteration.

Specify a boolean expression for the condition on LOOP to cause the loop to be executed only if the condition is true.  If the condition is false or missing before the loop contents are executed the first time, the loop contents are not executed at all.

If index and condition clauses are both present on LOOP, the index clause is always evaluated first.

Specify a boolean expression for the condition on END LOOP to cause the loop to terminate if the condition is not true after the enclosed code block is executed.  The condition is evaluated at the end of the loop, not at the beginning.

If the index clause and both condition clauses are not present, then the loop is executed MXLOOPS (see SET) times.

BREAK also terminates LOOP execution (see BREAK).

Statistics
**********

This chapter documents the statistical procedures that PSPP supports so far.

DESCRIPTIVES
============

     DESCRIPTIVES
             /VARIABLES=var_list
             /MISSING={VARIABLE,LISTWISE} {INCLUDE,NOINCLUDE}
             /FORMAT={LABELS,NOLABELS} {NOINDEX,INDEX} {LINE,SERIAL}
             /SAVE
             /STATISTICS={ALL,MEAN,SEMEAN,STDDEV,VARIANCE,KURTOSIS,
                          SKEWNESS,RANGE,MINIMUM,MAXIMUM,SUM,DEFAULT,
                          SESKEWNESS,SEKURTOSIS}
             /SORT={NONE,MEAN,SEMEAN,STDDEV,VARIANCE,KURTOSIS,SKEWNESS,
                    RANGE,MINIMUM,MAXIMUM,SUM,SESKEWNESS,SEKURTOSIS,NAME}
                   {A,D}

The DESCRIPTIVES procedure reads the active file and outputs descriptive statistics requested by the user.  In addition, it can optionally compute Z-scores.

The VARIABLES subcommand, which is required, specifies the list of variables to be analyzed.  Keyword VARIABLES is optional.

All other subcommands are optional:

The MISSING subcommand determines the handling of missing variables.  If INCLUDE is set, then user-missing values are included in the calculations.  If NOINCLUDE is set, which is the default, user-missing values are excluded.  If VARIABLE is set, then missing values are excluded on a variable by variable basis; if LISTWISE is set, then the entire case is excluded whenever any value in that case has a system-missing or, if INCLUDE is set, user-missing value.

The FORMAT subcommand affects the output format.  Currently the LABELS/NOLABELS and NOINDEX/INDEX settings are not used.  When SERIAL is set, both valid and missing number of cases are listed in the output; when NOSERIAL is set, only valid cases are listed.

The SAVE subcommand causes DESCRIPTIVES to calculate Z scores for all the specified variables.  The Z scores are saved to new variables. Variable names are generated by trying first the original variable name with Z prepended and truncated to a maximum of 8 characters, then the names ZSC000 through ZSC999, STDZ00 through STDZ09, ZZZZ00 through ZZZZ09, ZQZQ00 through ZQZQ09, in that sequence.  In addition, Z score variable names can be specified explicitly on VARIABLES in the variable list by enclosing them in parentheses after each variable.

The STATISTICS subcommand specifies the statistics to be displayed:

ALL
     All of the statistics below.

MEAN
     Arithmetic mean.

SEMEAN
     Standard error of the mean.

STDDEV
     Standard deviation.

VARIANCE
     Variance.

KURTOSIS
     Kurtosis and standard error of the kurtosis.

SKEWNESS
     Skewness and standard error of the skewness.

RANGE
     Range.

MINIMUM
     Minimum value.

MAXIMUM
     Maximum value.

SUM
     Sum.

DEFAULT
     Mean, standard deviation of the mean, minimum, maximum.

SEKURTOSIS
     Standard error of the kurtosis.

SESKEWNESS
     Standard error of the skewness.

The SORT subcommand specifies how the statistics should be sorted.  Most of the possible values should be self-explanatory.  NAME causes the statistics to be sorted by name.  By default, the statistics are listed in the order that they are specified on the VARIABLES subcommand.  The A and D settings request an ascending or descending sort order, respectively.

FREQUENCIES
===========

     FREQUENCIES
             /VARIABLES=var_list
             /FORMAT={TABLE,NOTABLE,LIMIT(limit)}
                     {STANDARD,CONDENSE,ONEPAGE[(onepage_limit)]}
                     {LABELS,NOLABELS}
                     {AVALUE,DVALUE,AFREQ,DFREQ}
                     {SINGLE,DOUBLE}
                     {OLDPAGE,NEWPAGE}
             /MISSING={EXCLUDE,INCLUDE}
             /STATISTICS={DEFAULT,MEAN,SEMEAN,MEDIAN,MODE,STDDEV,VARIANCE,
                          KURTOSIS,SKEWNESS,RANGE,MINIMUM,MAXIMUM,SUM,
                          SESKEWNESS,SEKURTOSIS,ALL,NONE}
             /NTILES=ntiles
             /PERCENTILES=percent...

     (These options are not currently implemented.)
             /BARCHART=...
             /HISTOGRAM=...
             /HBAR=...
             /GROUPED=...

     (Integer mode.)
             /VARIABLES=var_list (low,high)...

The FREQUENCIES procedure outputs frequency tables for specified variables. FREQUENCIES can also calculate and display descriptive statistics (including median and mode) and percentiles.

In the future, FREQUENCIES will also support graphical output in the form of bar charts and histograms.  In addition, it will be able to support percentiles for grouped data.

The VARIABLES subcommand is the only required subcommand.  Specify the variables to be analyzed.  In most cases, this is all that is required. This is known as general mode.

Occasionally, one may want to invoke a special mode called integer mode.  Normally, in general mode, PSPP will automatically determine what values occur in the data.  In integer mode, the user specifies the range of values that the data assumes.  To invoke this mode, specify a range of data values in parentheses, separated by a comma.  Data values inside the range are truncated to the nearest integer, then assigned to that value.  If values occur outside this range, they are discarded.

The FORMAT subcommand controls the output format.  It has several possible settings:

  * TABLE, the default, causes a frequency table to be output for every variable specified.  NOTABLE prevents them from being output.  LIMIT with a numeric argument causes them to be output except when there are more than the specified number of values in the table.

  * STANDARD frequency tables contain more complete information, but also to take up more space on the printed page.  CONDENSE frequency tables are less informative but take up less space.  ONEPAGE with a numeric argument will output standard frequency tables if there are the specified number of values or less, condensed tables otherwise.  ONEPAGE without an argument defaults to a threshold of 50 values.

  * LABELS causes value labels to be displayed in STANDARD frequency tables.  NOLABLES prevents this.

  * Normally frequency tables are sorted in ascending order by value.  This is AVALUE.  DVALUE tables are sorted in descending order by value. AFREQ and DFREQ tables are sorted in ascending and descending order, respectively, by frequency count.

  * SINGLE spaced frequency tables are closely spaced.  DOUBLE spaced frequency tables have wider spacing.

  * OLDPAGE and NEWPAGE are not currently used.

The MISSING subcommand controls the handling of user-missing values. When EXCLUDE, the default, is set, user-missing values are not included in frequency tables or statistics.  When INCLUDE is set, user-missing are included.  System-missing values are never included in statistics, but are listed in frequency tables.

The available STATISTICS are the same as available in DESCRIPTIVES (see DESCRIPTIVES), with the addition of MEDIAN, the data's median value, and MODE, the mode.  (If there are multiple modes, the smallest value is reported.)  By default, the mean, standard deviation of the mean, minimum, and maximum are reported for each variable.

NTILES causes the specified quartiles to be reported.  For instance, /NTILES=4 would cause quartiles to be reported.  In addition, particular percentiles can be requested with the PERCENTILES subcommand.

CROSSTABS
=========

     CROSSTABS
             /TABLES=var_list BY var_list [BY var_list]...
             /MISSING={TABLE,INCLUDE,REPORT}
             /WRITE={NONE,CELLS,ALL}
             /FORMAT={TABLES,NOTABLES}
                     {LABELS,NOLABELS,NOVALLABS}
                     {PIVOT,NOPIVOT}
                     {AVALUE,DVALUE}
                     {NOINDEX,INDEX}
                     {BOX,NOBOX}
             /CELLS={COUNT,ROW,COLUMN,TOTAL,EXPECTED,RESIDUAL,SRESIDUAL,
                     ASRESIDUAL,ALL,NONE}
             /STATISTICS={CHISQ,PHI,CC,LAMBDA,UC,BTAU,CTAU,RISK,GAMMA,D,
                          KAPPA,ETA,CORR,ALL,NONE}

     (Integer mode.)
             /VARIABLES=var_list (low,high)...

The CROSSTABS procedure displays crosstabulation tables requested by the user.  It can calculate several statistics for each cell in the crosstabulation tables.  In addition, a number of statistics can be calculated for each table itself.

The TABLES subcommand is used to specify the tables to be reported.  Any number of dimensions is permitted, and any number of variables per dimension is allowed.  The TABLES subcommand may be repeated as many times as needed.  This is the only required subcommand in general mode.

Occasionally, one may want to invoke a special mode called integer mode.  Normally, in general mode, PSPP automatically determines what values occur in the data.  In integer mode, the user specifies the range of values that the data assumes.  To invoke this mode, specify the VARIABLES subcommand, giving a range of data values in parentheses for each variable to be used on the TABLES subcommand.  Data values inside the range are truncated to the nearest integer, then assigned to that value.  If values occur outside this range, they are discarded.  When it is present, the VARIABLES subcommand must precede the TABLES subcommand.

In general mode, numeric and string variables may be specified on TABLES.  Although long string variables are allowed, only their initial short-string parts are used.  In integer mode, only numeric variables are allowed.

The MISSING subcommand determines the handling of user-missing values. When set to TABLE, the default, missing values are dropped on a table by table basis.  When set to INCLUDE, user-missing values are included in tables and statistics.  When set to REPORT, which is allowed only in integer mode, user-missing values are included in tables but marked with an M (for ``missing'') and excluded from statistical calculations.

Currently the WRITE subcommand is ignored.

The FORMAT subcommand controls the characteristics of the crosstabulation tables to be displayed.  It has a number of possible settings:

  * TABLES, the default, causes crosstabulation tables to be output. NOTABLES suppresses them.

  * LABELS, the default, allows variable labels and value labels to appear in the output.  NOLABELS suppresses them.  NOVALLABS displays variable labels but suppresses value labels.

  * PIVOT, the default, causes each TABLES subcommand to be displayed in a pivot table format.  NOPIVOT causes the old-style crosstabulation format to be used.

  * AVALUE, the default, causes values to be sorted in ascending order. DVALUE asserts a descending sort order.

  * INDEX/NOINDEX is currently ignored.

  * BOX/NOBOX is currently ignored.

The CELLS subcommand controls the contents of each cell in the displayed crosstabulation table.  The possible settings are:

COUNT
     Frequency count.

ROW
     Row percent.

COLUMN
     Column percent.

TOTAL
     Table percent.

EXPECTED
     Expected value.

RESIDUAL
     Residual.

SRESIDUAL
     Standardized residual.

ASRESIDUAL
     Adjusted standardized residual.

ALL
     All of the above.

NONE
     Suppress cells entirely.

/CELLS without any settings specified requests COUNT, ROW, COLUMN, and TOTAL.  If CELLS is not specified at all then only COUNT will be selected.

The STATISTICS subcommand selects statistics for computation:

CHISQ
     Pearson chi-square, likelihood ratio, Fisher's exact test, continuity correction, linear-by-linear association.

PHI
     Phi.

CC
     Contingency coefficient.

LAMBDA
     Lambda.

UC
     Uncertainty coefficient.

BTAU
     Tau-b.

CTAU
     Tau-c.

RISK
     Risk estimate.

GAMMA
     Gamma.

D
     Somers' D.

KAPPA
     Cohen's Kappa.

ETA
     Eta.

CORR
     Spearman correlation, Pearson's r.

ALL
     All of the above.

NONE
     No statistics.

Selected statistics are only calculated when appropriate for the statistic.  Certain statistics require tables of a particular size, and some statistics are calculated only in integer mode.

/STATISTICS without any settings selects CHISQ.  If the STATISTICS subcommand is not given, no statistics are calculated.

Please note: Currently the implementation of CROSSTABS has the followings bugs:

  * Pearson's R (but not Spearman) is off a little.

  * T values for Spearman's R and Pearson's R are wrong.

  * Significance of symmetric and directional measures is not calculated.

  * Asymmetric ASEs and T values for lambda are wrong.

  * ASE of Goodman and Kruskal's tau is not calculated.

  * ASE of symmetric somers' d is wrong.

  * Approximate T of uncertainty coefficient is wrong.

Fixes for any of these deficiencies would be welcomed.

T-TEST
======

     T-TEST
             /MISSING={ANALYSIS,LISTWISE} {EXCLUDE,INCLUDE}
             /CRITERIA=CIN(confidence)

     (One Sample mode.)
             TESTVAL=test_value
             /VARIABLES=var_list

     (Independent Samples mode.)
             GROUPS=var(value1 [, value2])
             /VARIABLES=var_list

     (Paired Samples mode.)
             PAIRS=var_list [WITH var_list [(PAIRED)] ]

The T-TEST procedure outputs tables used in testing hypotheses about means. It operates in one of three modes:

  * One Sample mode.

  * Independent Groups mode.

  * Paired mode.

Each of these modes are described in more detail below. There are two optional subcommands which are common to all modes.

The /CRITERIA subcommand tells PSPP the confidence interval used in the tests.  The default value is 0.95.

The MISSING subcommand determines the handling of missing variables. If INCLUDE is set, then user-missing values are included in the calculations, but system-missing values are not. If EXCLUDE is set, which is the default, user-missing values are excluded as well as system-missing values. This is the default.

If LISTWISE is set, then the entire case is excluded from analysis whenever any variable  specified in the /VARIABLES, /PAIRS or /GROUPS subcommands contains a missing value. If ANALYSIS is set, then missing values are excluded only in the analysis for which they would be needed. This is the default.

One Sample Mode
---------------

The TESTVAL subcommand invokes the One Sample mode. This mode is used to test a population mean against a hypothesised mean. The value given to the TESTVAL subcommand is the value against which you wish to test. In this mode, you must also use the /VARIABLES subcommand to tell PSPP which variables you wish to test.

Independent Samples Mode
------------------------

The GROUPS subcommand invokes Independent Samples mode or `Groups' mode. This mode is used to test whether two groups of values have the same population mean. In this mode, you must also use the /VARIABLES subcommand to tell PSPP the dependent variables you wish to test.

The variable given in the GROUPS subcommand is the independent variable which determines to which group the samples belong. The values in parentheses are the specific values of the independent variable for each group. If the parentheses are omitted and no values are given, the default values of 1.0 and 2.0 are assumed.

If the independent variable is numeric, it is acceptable to specify only one value inside the parentheses. If you do this, cases where the independent variable is less than  or equal to this value belong to the first group, and cases greater than this value belong to the second group. When using this form of the GROUPS subcommand, missing values in the independent variable are excluded on a listwise basis, regardless of whether /MISSING=LISTWISE was specified.

Paired Samples Mode
-------------------

The PAIRS subcommand introduces Paired Samples mode. Use this mode when repeated measures have been taken from the same samples. If the the WITH keyword is omitted, then tables for all combinations of variables given in the PAIRS subcommand are generated. If the WITH keyword is given, and the (PAIRED) keyword is also given, then the number of variables preceding WITH must be the same as the number following it. In this case, tables for each respective pair of variables are generated. In the event that the WITH keyword is given, but the (PAIRED) keyword is omitted, then tables for each combination of variable preceding WITH against variable following WITH are generated.

Utilities
*********

Commands that don't fit any other category are placed here.

Most of these commands are not affected by commands like IF and LOOP: they take effect only once, unconditionally, at the time that they are encountered in the input.

COMMENT
=======

     Two possibles syntaxes:
             COMMENT comment text ... .
             *comment text ... .

COMMENT is ignored.  It is used to provide information to the author and other readers of the PSPP syntax file.

COMMENT can extend over any number of lines.  Don't forget to terminate it with a dot or a blank line.

DOCUMENT
========

     DOCUMENT documentary_text.

DOCUMENT adds one or more lines of descriptive commentary to the active file.  Documents added in this way are saved to system files. They can be viewed using SYSFILE INFO or DISPLAY
DOCUMENTS.  They can be removed from the active file with DROP
DOCUMENTS.

Specify the documentary text following the DOCUMENT keyword.  You can extend the documentary text over as many lines as necessary.  Lines are truncated at 80 characters width.  Don't forget to terminate the command with a dot or a blank line.

DISPLAY DOCUMENTS
=================

     DISPLAY DOCUMENTS.

DISPLAY DOCUMENTS displays the documents in the active file.  Each document is preceded by a line giving the time and date that it was added.  See DOCUMENT.

DISPLAY FILE LABEL
==================

     DISPLAY FILE LABEL.

DISPLAY FILE LABEL displays the file label contained in the active file, if any.  See FILE LABEL.

DROP DOCUMENTS
==============

     DROP DOCUMENTS.

DROP DOCUMENTS removes all documents from the active file. New documents can be added with DOCUMENT (see DOCUMENT).

DROP DOCUMENTS changes only the active file.  It does not modify any system files stored on disk.

ERASE
=====

     ERASE FILE file_name.

ERASE FILE deletes a file from the local filesystem. file_name must be quoted. This command cannot be used if the SAFER setting is active.

EXECUTE
=======

     EXECUTE.

EXECUTE causes the active file to be read and all pending transformations to be executed.

FILE LABEL
==========

     FILE LABEL file_label.

FILE LABEL provides a title for the active file.  This title will be saved into system files and portable files that are created during this PSPP run.

file_label need not be quoted.  If quotes are included, they become part of the file label.

FINISH
======

     FINISH.

FINISH terminates the current PSPP session and returns control to the operating system.

This command is not valid in interactive mode.

HOST
====

     HOST.

HOST suspends the current PSPP session and temporarily returns control to the operating system. This command cannot be used if the SAFER setting is active.

INCLUDE
=======

     Two possible syntaxes:
             INCLUDE 'filename'.
             @filename.

INCLUDE causes the PSPP command processor to read an additional command file as if it were included bodily in the current command file.

Include files may be nested to any depth, up to the limit of available memory.

QUIT
====

     Two possible syntaxes:
             QUIT.
             EXIT.

QUIT terminates the current PSPP session and returns control to the operating system.

This command is not valid within a command file.

SET
===

     SET

     (data input)
             /BLANKS={SYSMIS,'.',number}
             /DECIMAL={DOT,COMMA}
             /FORMAT=fmt_spec

     (program input)
             /ENDCMD='.'
             /NULLINE={ON,OFF}

     (interaction)
             /CPROMPT='cprompt_string'
             /DPROMPT='dprompt_string'
             /ERRORBREAK={OFF,ON}
             /MXERRS=max_errs
             /MXWARNS=max_warnings
             /PROMPT='prompt'
             /VIEWLENGTH={MINIMUM,MEDIAN,MAXIMUM,n_lines}
             /VIEWWIDTH=n_characters

     (program execution)
             /MEXPAND={ON,OFF}
             /MITERATE=max_iterations
             /MNEST=max_nest
             /MPRINT={ON,OFF}
             /MXLOOPS=max_loops
             /SEED={RANDOM,seed_value}
             /UNDEFINED={WARN,NOWARN}

     (data output)
             /CC{A,B,C,D,E}={'npre,pre,suf,nsuf','npre.pre.suf.nsuf'}
             /DECIMAL={DOT,COMMA}
             /FORMAT=fmt_spec

     (output routing)
             /ECHO={ON,OFF}
             /ERRORS={ON,OFF,TERMINAL,LISTING,BOTH,NONE}
             /INCLUDE={ON,OFF}
             /MESSAGES={ON,OFF,TERMINAL,LISTING,BOTH,NONE}
             /PRINTBACK={ON,OFF}
             /RESULTS={ON,OFF,TERMINAL,LISTING,BOTH,NONE}

     (output activation)
             /LISTING={ON,OFF}
             /PRINTER={ON,OFF}
             /SCREEN={ON,OFF}

     (output driver options)
             /HEADERS={NO,YES,BLANK}
             /LENGTH={NONE,length_in_lines}
             /LISTING=filename
             /MORE={ON,OFF}
             /PAGER={OFF,"pager_name"}
             /WIDTH={NARROW,WIDTH,n_characters}

     (logging)
             /JOURNAL={ON,OFF} [filename]
             /LOG={ON,OFF} [filename]

     (system files)
             /COMPRESSION={ON,OFF}
             /SCOMPRESSION={ON,OFF}

     (security)
             /SAFER=ON

     (obsolete settings accepted for compatibility, but ignored)
             /AUTOMENU={ON,OFF}
             /BEEP={ON,OFF}
             /BLOCK='c'
             /BOXSTRING={'xxx','xxxxxxxxxxx'}
             /CASE={UPPER,UPLOW}
             /COLOR=...
             /CPI=cpi_value
             /DISK={ON,OFF}
             /EJECT={ON,OFF}
             /HELPWINDOWS={ON,OFF}
             /HIGHRES={ON,OFF}
             /HISTOGRAM='c'
             /LOWRES={AUTO,ON,OFF}
             /LPI=lpi_value
             /MENUS={STANDARD,EXTENDED}
             /MXMEMORY=max_memory
             /PTRANSLATE={ON,OFF}
             /RCOLORS=...
             /RUNREVIEW={AUTO,MANUAL}
             /SCRIPTTAB='c'
             /TB1={'xxx','xxxxxxxxxxx'}
             /TBFONTS='string'
             /WORKDEV=drive_letter
             /WORKSPACE=workspace_size
             /XSORT={YES,NO}

SET allows the user to adjust several parameters relating to PSPP's execution.  Since there are many subcommands to this command, its subcommands will be examined in groups.

On subcommands that take boolean values, ON and YES are synonym, and as are OFF and NO, when used as subcommand values.

The data input subcommands affect the way that data is read from data files.  The data input subcommands are

BLANKS
     This is the value assigned to an item data item that is empty or contains only whitespace.  An argument of SYSMIS or '.' will cause the system-missing value to be assigned to null items.  This is the default.  Any real value may be assigned.

DECIMAL
     The default DOT setting causes the decimal point character to be ..  A setting of COMMA causes the decimal point character to be ,.

FORMAT
     Allows the default numeric input/output format to be specified.  The default is F8.2.  See Input/Output Formats.

Program input subcommands affect the way that programs are parsed when they are typed interactively or run from a script.  They are

ENDCMD
     This is a single character indicating the end of a command.  The default is ..  Don't change this.

NULLINE
     Whether a blank line is interpreted as ending the current command.  The default is ON.

Interaction subcommands affect the way that PSPP interacts with an online user.  The interaction subcommands are

CPROMPT
     The command continuation prompt.  The default is     > .

DPROMPT
     Prompt used when expecting data input within BEGIN DATA (see BEGIN DATA).  The default is data> .

ERRORBREAK
     Whether an error causes PSPP to stop processing the current command file after finishing the current command.  The default is OFF.

MXERRS
     The maximum number of errors before PSPP halts processing of the current command file.  The default is 50.

MXWARNS
     The maximum number of warnings + errors before PSPP halts processing the current command file.  The default is 100.

PROMPT
     The command prompt.  The default is PSPP> .

VIEWLENGTH
     The length of the screen in lines.  MINIMUM means 25 lines, MEDIAN and MAXIMUM mean 43 lines.  Otherwise specify the number of lines.  Normally PSPP should auto-detect your screen size so this shouldn't have to be used.

VIEWWIDTH
     The width of the screen in characters.  Normally 80 or 132.

Program execution subcommands control the way that PSPP commands execute.  The program execution subcommands are

MEXPAND
MITERATE
MNEST
MPRINT
     Currently not used.

MXLOOPS
     The maximum number of iterations for an uncontrolled loop (see LOOP).

SEED
     The initial pseudo-random number seed.  Set to a real number or to RANDOM, which will obtain an initial seed from the current time of day.

UNDEFINED
     Currently not used.

Data output subcommands affect the format of output data.  These subcommands are

CCA
CCB
CCC
CCD
CCE
     Set up custom currency formats.  The argument is a string which must contain exactly three commas or exactly three periods.  If commas, then the grouping character for the currency format is ,, and the decimal point character is .; if periods, then the situation is reversed.

     The commas or periods divide the string into four fields, which are, in order, the negative prefix, prefix, suffix, and negative suffix.  When a value is formatted using the custom currency format, the prefix precedes the value formatted and the suffix follows it.  In addition, if the value is negative, the negative prefix precedes the prefix and the negative suffix follows the suffix.

DECIMAL
     The default DOT setting causes the decimal point character to be ..  A setting of COMMA causes the decimal point character to be ,.

FORMAT
     Allows the default numeric input/output format to be specified.  The default is F8.2.  See Input/Output Formats.

Output routing subcommands affect where the output of transformations and procedures is sent.  These subcommands are

ECHO

     If turned on, commands are written to the listing file as they are read from command files.  The default is OFF.

ERRORS
INCLUDE
MESSAGES

PRINTBACK

RESULTS
     Currently not used.

Output activation subcommands affect whether output devices of particular types are enabled.  These subcommands are

LISTING
     Enable or disable listing devices.

PRINTER
     Enable or disable printer devices.

SCREEN
     Enable or disable screen devices.

Output driver option subcommands affect output drivers' settings.  These subcommands are

HEADERS
LENGTH
LISTING
MORE
PAGER
WIDTH
     Currently not used.

Logging subcommands affect logging of commands executed to external files.  These subcommands are

JOURNAL

LOG
     Not currently used.

System file subcommands affect the default format of system files produced by PSPP.  These subcommands are

COMPRESSION
     Not currently used.

SCOMPRESSION
     Whether system files created by SAVE or XSAVE are compressed by default.  The default is ON.

Security subcommands affect the operations that commands are allowed to perform.  The security subcommands are

SAFER
     When set, this setting cannot ever be reset, for obvious security reasons.  Setting this option disables the following operations:

       * The ERASE command.

       * The HOST command.

       * Pipe filenames (filenames beginning or ending with |).

     Be aware that this setting does not guarantee safety (commands can still overwrite files, for instance) but it is an improvement.

SUBTITLE
========

     SUBTITLE 'subtitle_string'.
       or
     SUBTITLE subtitle_string.

SUBTITLE provides a subtitle to a particular PSPP run.  This subtitle appears at the top of each output page below the title, if headers are enabled on the output device.

Specify a subtitle as a string in quotes.  The alternate syntax that did not require quotes is now obsolete.  If it is used then the subtitle is converted to all uppercase.

TITLE
=====

     TITLE 'title_string'.
       or
     TITLE title_string.

TITLE provides a title to a particular PSPP run. This title appears at the top of each output page, if headers are enabled on the output device.

Specify a title as a string in quotes.  The alternate syntax that did not require quotes is now obsolete.  If it is used then the title is converted to all uppercase.

Not Implemented
***************

This chapter lists parts of the PSPP language that are not yet implemented.

The following transformations and utilities are not yet implemented, but they will be supported in a later release.

  * ADD FILES

  * ANOVA

  * DEFINE

  * FILE TYPE

  * GET SAS

  * GET TRANSLATE

  * MCONVERT

  * PLOT

  * PRESERVE

  * PROCEDURE OUTPUT

  * RESTORE

  * SAVE TRANSLATE

  * SHOW

  * UPDATE

The following transformations and utilities are not implemented.  There are no plans to support them in future releases.  Contributions to implement them will still be accepted.

  * EDIT

  * GET DATABASE

  * GET OSIRIS

  * GET SCSS

  * GSET

  * HELP

  * INFO

  * INPUT MATRIX

  * KEYED DATA LIST

  * NUMBERED and UNNUMBERED

  * OPTIONS

  * REVIEW

  * SAVE SCSS

  * SPSS MANAGER

  * STATISTICS

Data File Format
****************

PSPP necessarily uses the same format for system files as do the products with which it is compatible.  This chapter is a description of that format.

There are three data types used in system files: 32-bit integers, 64-bit floating points, and 1-byte characters.  In this document these will simply be referred to as int32, flt64, and char, the names that are used in the PSPP source code.  Every field of type int32 or flt64 is aligned on a 32-bit boundary.

The endianness of data in PSPP system files is not specified.  System files output on a computer of a particular endianness will have the endianness of that computer.  However, PSPP can read files of either endianness, regardless of its host computer's endianness.  PSPP translates endianness for both integer and floating point numbers.

Floating point formats are also not specified.  PSPP does not translate between floating point formats.  This is unlikely to be a problem as all modern computer architectures use IEEE 754 format for floating point representation.

The PSPP system-missing value is represented by the largest possible negative number in the floating point format; in C, this is most likely -DBL_MAX.  There are two other important values used in missing values: HIGHEST and LOWEST.  These are represented by the largest possible positive number (probably DBL_MAX) and the second-largest negative number.  The latter must be determined in a system-dependent manner; in IEEE 754 format it is represented by value 0xffeffffffffffffe.

System files are divided into records.  Each record begins with an int32 giving a numeric record type.  Individual record types are described below:

File Header Record
==================

The file header is always the first record in the file.

     struct sysfile_header
       {
         char                rec_type[4];
         char                prod_name[60];
         int32               layout_code;
         int32               case_size;
         int32               compressed;
         int32               weight_index;
         int32               ncases;
         flt64               bias;
         char                creation_date[9];
         char                creation_time[8];
         char                file_label[64];
         char                padding[3];
       };

char rec_type[4];
     Record type code.  Always set to $FL2.  This is the only record for which the record type is not of type int32.

char prod_name[60];
     Product identification string.  This always begins with the characters @(#) SPSS DATA FILE.  PSPP uses the remaining characters to give its version and the operating system name; for example, GNU pspp 0.1.4 - sparc-sun-solaris2.5.2.  The string is truncated if it would be longer than 60 characters; otherwise it is padded on the right with spaces.

int32 layout_code;
     Always set to 2.  PSPP reads this value to determine the file's endianness.

int32 case_size;
     Number of data elements per case.  This is the number of variables, except that long string variables add extra data elements (one for every 8 characters after the first 8).

int32 compressed;
     Set to 1 if the data in the file is compressed, 0 otherwise.

int32 weight_index;
     If one of the variables in the data set is used as a weighting variable, set to the index of that variable.  Otherwise, set to 0.

int32 ncases;
     Set to the number of cases in the file if it is known, or -1 otherwise.

     In the general case it is not possible to determine the number of cases that will be output to a system file at the time that the header is written.  The way that this is dealt with is by writing the entire system file, including the header, then seeking back to the beginning of the file and writing just the ncases field.  For `files' in which this is not valid, the seek operation fails.  In this case, ncases remains -1.

flt64 bias;
     Compression bias.  Always set to 100.  The significance of this value is that only numbers between (1 - bias) and (251 - bias) can be compressed.

char creation_date[9];
     Set to the date of creation of the system file, in dd mmm yy format, with the month as standard English abbreviations, using an initial capital letter and following with lowercase.  If the date is not available then this field is arbitrarily set to 01 Jan 70.

char creation_time[8];
     Set to the time of creation of the system file, in hh:mm:ss format and using 24-hour time.  If the time is not available then this field is arbitrarily set to 00:00:00.

char file_label[64];
     Set the the file label declared by the user, if any.  Padded on the right with spaces.

char padding[3];
     Ignored padding bytes to make the structure a multiple of 32 bits in length.  Set to zeros.

Variable Record
===============

Immediately following the header must come the variable records.  There must be one variable record for every variable and every 8 characters in a long string beyond the first 8; i.e., there must be exactly as many variable records as the value specified for case_size in the file header record.

     struct sysfile_variable
       {
         int32               rec_type;
         int32               type;
         int32               has_var_label;
         int32               n_missing_values;
         int32               print;
         int32               write;
         char                name[8];

         /* The following two fields are present
            only if has_var_label is 1. */
         int32               label_len;
         char                label[/* variable length */];

         /* The following field is present only
            if n_missing_values is not 0. */
         flt64               missing_values[/* variable length*/];
       };

int32 rec_type;
     Record type code.  Always set to 2.

int32 type;
     Variable type code.  Set to 0 for a numeric variable.  For a short string variable or the first part of a long string variable, this is set to the width of the string.  For the second and subsequent parts of a long string variable, set to -1, and the remaining fields in the structure are ignored.

int32 has_var_label;
     If this variable has a variable label, set to 1; otherwise, set to 0.

int32 n_missing_values;
     If the variable has no missing values, set to 0.  If the variable has one, two, or three discrete missing values, set to 1, 2, or 3, respectively.  If the variable has a range for missing variables, set to -2; if the variable has a range for missing variables plus a single discrete value, set to -3.

int32 print;
     Print format for this variable.  See below.

int32 write;
     Write format for this variable.  See below.

char name[8];
     Variable name.  The variable name must begin with a capital letter or the at-sign (@).  Subsequent characters may also be octothorpes (#), dollar signs ($), underscores (_), or full stops (.).  The variable name is padded on the right with spaces.

int32 label_len;
     This field is present only if has_var_label is set to 1.  It is set to the length, in characters, of the variable label, which must be a number between 0 and 120.

char label[/* variable length */];
     This field is present only if has_var_label is set to 1.  It has length label_len, rounded up to the nearest multiple of 32 bits. The first label_len characters are the variable's variable label.

flt64 missing_values[/* variable length */];
     This field is present only if n_missing_values is not 0.  It has the same number of elements as the absolute value of n_missing_values.  For discrete missing values, each element represents one missing value.  When a range is present, the first element denotes the minimum value in the range, and the second element denotes the maximum value in the range.  When a range plus a value are present, the third element denotes the additional discrete missing value.  HIGHEST and LOWEST are indicated as described in the chapter introduction.

The print and write members of sysfile_variable are output formats coded into int32 types.  The LSB (least-significant byte) of the int32 represents the number of decimal places, and the next two bytes in order of increasing significance represent field width and format type, respectively.  The MSB (most-significant byte) is not used and should be set to zero.

Format types are defined as follows:

0
     Not used.

1
     A

2
     AHEX

3
     COMMA

4
     DOLLAR

5
     F

6
     IB

7
     PIBHEX

8
     P

9
     PIB

10
     PK

11
     RB

12
     RBHEX

13
     Not used.

14
     Not used.

15
     Z

16
     N

17
     E

18
     Not used.

19
     Not used.

20
     DATE

21
     TIME

22
     DATETIME

23
     ADATE

24
     JDATE

25
     DTIME

26
     WKDAY

27
     MONTH

28
     MOYR

29
     QYR

30
     WKYR

31
     PCT

32
     DOT

33
     CCA

34
     CCB

35
     CCC

36
     CCD

37
     CCE

38
     EDATE

39
     SDATE

Value Label Record
==================

Value label records must follow the variable records and must precede the header termination record.  Other than this, they may appear anywhere in the system file.  Every value label record must be immediately followed by a label variable record, described below.

Value label records begin with rec_type, an int32 value set to the record type of 3.  This is followed by count, an int32 value set to the number of value labels present in this record.

These two fields are followed by a series of count tuples.  Each tuple is divided into two fields, the value and the label.  The first of these, the value, is composed of a 64-bit value, which is either a flt64 value or up to 8 characters (padded on the right to 8 bytes) denoting a short string value.  Whether the value is a flt64 or a character string is not defined inside the value label record.

The second field in the tuple, the label, has variable length.  The first char is a count of the number of characters in the value label.  The remainder of the field is the label itself.  The field is padded on the right to a multiple of 64 bits in length.

Value Label Variable Record
===========================

Every value label variable record must be immediately preceded by a value label record, described above.

     struct sysfile_value_label_variable
       {
          int32              rec_type;
          int32              count;
          int32              vars[/* variable length */];
       };

int32 rec_type;
     Record type.  Always set to 4.

int32 count;
     Number of variables that the associated value labels from the value label record are to be applied.

int32 vars[/* variable length];
     A list of variables to which to apply the value labels.  There are count elements.

Document Record
===============

There must be no more than one document record per system file. Document records must follow the variable records and precede the dictionary termination record.

     struct sysfile_document
       {
         int32               rec_type;
         int32               n_lines;
         char                lines[/* variable length */][80];
       };

int32 rec_type;
     Record type.  Always set to 6.

int32 n_lines;
     Number of lines of documents present.

char lines[/* variable length */][80];
     Document lines.  The number of elements is defined by n_lines. Lines shorter than 80 characters are padded on the right with spaces.

Machine int32 Info Record
=========================

There must be no more than one machine int32 info record per system file.  Machine int32 info records must follow the variable records and precede the dictionary termination record.

     struct sysfile_machine_int32_info
       {
         /* Header. */
         int32               rec_type;
         int32               subtype;
         int32               size;
         int32               count;

         /* Data. */
         int32               version_major;
         int32               version_minor;
         int32               version_revision;
         int32               machine_code;
         int32               floating_point_rep;
         int32               compression_code;
         int32               endianness;
         int32               character_code;
       };

int32 rec_type;
     Record type.  Always set to 7.

int32 subtype;
     Record subtype.  Always set to 3.

int32 size;
     Size of each piece of data in the data part, in bytes.  Always set to 4.

int32 count;
     Number of pieces of data in the data part.  Always set to 8.

int32 version_major;
     PSPP major version number.  In version X.Y.Z, this is X.

int32 version_minor;
     PSPP minor version number.  In version X.Y.Z, this is Y.

int32 version_revision;
     PSPP version revision number.  In version X.Y.Z, this is Z.

int32 machine_code;
     Machine code.  PSPP always set this field to value to -1, but other values may appear.

int32 floating_point_rep;
     Floating point representation code.  For IEEE 754 systems this is 1. IBM 370 sets this to 2, and DEC VAX E to 3.

int32 compression_code;
     Compression code.  Always set to 1.

int32 endianness;
     Machine endianness.  1 indicates big-endian, 2 indicates little-endian.

int32 character_code;
     Character code.  1 indicates EBCDIC, 2 indicates 7-bit ASCII, 3 indicates 8-bit ASCII, 4 indicates DEC Kanji.

Machine flt64 Info Record
=========================

There must be no more than one machine flt64 info record per system file.  Machine flt64 info records must follow the variable records and precede the dictionary termination record.

     struct sysfile_machine_flt64_info
       {
         /* Header. */
         int32               rec_type;
         int32               subtype;
         int32               size;
         int32               count;

         /* Data. */
         flt64               sysmis;
         flt64               highest;
         flt64               lowest;
       };

int32 rec_type;
     Record type.  Always set to 3.

int32 subtype;
     Record subtype.  Always set to 4.

int32 size;
     Size of each piece of data in the data part, in bytes.  Always set to 4.

int32 count;
     Number of pieces of data in the data part.  Always set to 3.

flt64 sysmis;
     The system missing value.

flt64 highest;
     The value used for HIGHEST in missing values.

flt64 lowest;
     The value used for LOWEST in missing values.

Miscellaneous Informational Records
===================================

Miscellaneous informational records must follow the variable records and precede the dictionary termination record.

Miscellaneous informational records are ignored by PSPP when reading system files.  They are not written by PSPP when writing system files.

     struct sysfile_misc_info
       {
         /* Header. */
         int32               rec_type;
         int32               subtype;
         int32               size;
         int32               count;

         /* Data. */
         char                data[/* variable length */];
       };

int32 rec_type;
     Record type.  Always set to 3.

int32 subtype;
     Record subtype.  May take any value.

int32 size;
     Size of each piece of data in the data part.  Should have the value 4 or 8, for int32 and flt64, respectively.

int32 count;
     Number of pieces of data in the data part.

char data[/* variable length */];
     Arbitrary data.  There must be size times count bytes of data.

Dictionary Termination Record
=============================

The dictionary termination record must follow all other records, except for the actual cases, which it must precede.  There must be exactly one dictionary termination record in every system file.

     struct sysfile_dict_term
       {
         int32               rec_type;
         int32               filler;
       };

int32 rec_type;
     Record type.  Always set to 999.

int32 filler;
     Ignored padding.  Should be set to 0.

Data Record
===========

Data records must follow all other records in the data file.  There must be at least one data record in every system file.

The format of data records varies depending on whether the data is compressed.  Regardless, the data is arranged in a series of 8-byte elements.

When data is not compressed, Every case is composed of case_size of these 8-byte elements, where case_size comes from the file header record (see File Header Record).  Each element corresponds to the variable declared in the respective variable record (see Variable Record).  Numeric values are given in flt64 format; string values are literal characters string, padded on the right when necessary.

Compressed data is arranged in the following manner: the first 8-byte element in the data section is divided into a series of 1-byte command codes.  These codes have meanings as described below:

0
     Ignored.  If the program writing the system file accumulates compressed data in blocks of fixed length, 0 bytes can be used to pad out extra bytes remaining at the end of a fixed-size block.

1 through 251
     These values indicate that the corresponding numeric variable has the value (CODE - BIAS) for the case being read, where CODE is the value of the compression code and BIAS is the variable compression_bias from the file header.  For example, code 105 with bias 100.0 (the normal value) indicates a numeric variable of value 5.

252
     End of file.  This code may or may not appear at the end of the data stream.  PSPP always outputs this code but its use is not required.

253
     This value indicates that the numeric or string value is not compressible.  The value is stored in the 8-byte element following the current block of command bytes.  If this value appears twice in a block of command bytes, then it indicates the second element following the command bytes, and so on.

254
     Used to indicate a string value that is all spaces.

255
     Used to indicate the system-missing value.

When the end of the first 8-byte element of command bytes is reached, any blocks of non-compressible values are skipped, and the next element of command bytes is read and interpreted, until the end of the file is reached.

Portable File Format
********************

These days, most computers use the same internal data formats for integer and floating-point data, if one ignores little differences like big- versus little-endian byte ordering.  However, occasionally it is necessary to exchange data between systems with incompatible data formats.  This is what portable files are designed to do.

Please note: Although all of the following information is correct, as far as the author has been able to ascertain, it is gleaned from examination of ASCII-formatted portable files only, so some of it may be incorrect in the general case.

Portable File Characters
========================

Portable files are arranged as a series of lines of exactly 80 characters each.  Each line is terminated by a carriage-return, line-feed sequence (henceforth, ``newline'').  Newlines are not delimiters: they are only used to avoid line-length limitations existing on some operating systems.

The file must be terminated with a Z character.  In addition, if the final line in the file does not have exactly 80 characters, then it is padded on the right with Z characters.  (The file contents may be in any character set; the file contains a description of its own character set, as explained in the next section.  Therefore, the Z character is not necessarily an ASCII Z.)

For the rest of the description of the portable file format, newlines and the trailing Zs will be ignored, as if they did not exist, because they are not an important part of understanding the file contents.

Portable File Structure
=======================

Every portable file consists of the following records, in sequence:

  * File header.

  * Version and date info.

  * Product identification.

  * Subproduct identification (optional).

  * Variable count.

  * Variables.  Each variable record may optionally be followed by a missing value record and a variable label record.

  * Value labels (optional).

  * Data.

Most records are identified by a single-character tag code.  The file header and version info record do not have a tag.

Other than these single-character codes, there are three types of fields in a portable file: floating-point, integer, and string.  Floating-point fields have the following format:

  * Zero or more leading spaces.

  * Optional asterisk (*), which indicates a missing value.  The asterisk must be followed by a single character, generally a period (.), but it appears that other characters may also be possible. This completes the specification of a missing value.

  * Optional minus sign (-) to indicate a negative number.

  * A whole number, consisting of one or more base-30 digits: 0 through 9 plus capital letters A through T.

  * A fraction, consisting of a radix point (.) followed by one or more base-30 digits (optional).

  * An exponent, consisting of a plus or minus sign (+ or -) followed by one or more base-30 digits (optional).

  * A forward slash (/).

Integer fields take form identical to floating-point fields, but they may not contain a fraction.

String fields take the form of a integer field having value N, followed by exactly N characters, which are the string content.

Portable File Header
====================

Every portable file begins with a 464-byte header, consisting of a 200-byte collection of vanity splash strings, followed by a 256-byte character set translation table, followed by an 8-byte tag string.

The 200-byte segment is divided into five 40-byte sections, each of which represents the string ASCII SPSS PORT FILE in a different character set encoding.  (If the file is encoded in EBCDIC then the string is actually EBCDIC SPSS PORT FILE, and so on.)  These strings are padded on the right with spaces in their own character set.

It appears that these strings exist only to inform those who might view the file on a screen, and that they are not parsed by SPSS products. Thus, they can be safely ignored.  For those interested, the strings are supposed to be in the following character sets, in the specified order: EBCDIC, 7-bit ASCII, CDC 6-bit ASCII, 6-bit ASCII, Honeywell 6-bit ASCII.

The 256-byte segment describes a mapping from the character set used in the portable file to an arbitrary character set having characters at the following positions:

0--60

     Control characters.  Not important enough to describe in full here.

61--63

     Reserved.

64--73

     Digits 0 through 9.

74--99

     Capital letters A through Z.

100--125

     Lowercase letters a through z.

126

     Space.

127--130

     Symbols .<(+

131

     Solid vertical pipe.

132--142

     Symbols &[]!$*);^-/

143

     Broken vertical pipe.

144--150

     Symbols ,%_>?`:

151

     British pound symbol.

152--155

     Symbols @'=".

156

     Less than or equal symbol.

157

     Empty box.

158

     Plus or minus.

159

     Filled box.

160

     Degree symbol.

161

     Dagger.

162

     Symbol ~.

163

     En dash.

164

     Lower left corner box draw.

165

     Upper left corner box draw.

166

     Greater than or equal symbol.

167--176

     Superscript 0 through 9.

177

     Lower right corner box draw.

178

     Upper right corner box draw.

179

     Not equal symbol.

180

     Em dash.

181

     Superscript (.

182

     Superscript ).

183

     Horizontal dagger (?).

184--186

     Symbols {}\.

187

     Cents symbol.

188

     Centered dot, or bullet.

189--255

     Reserved.

Symbols that are not defined in a particular character set are set to the same value as symbol 64; i.e., to 0.

The 8-byte tag string consists of the exact characters SPSSPORT in the portable file's character set, which can be used to verify that the file is indeed a portable file.

Version and Date Info Record
============================

This record does not have a tag code.  It has the following structure:

  * A single character identifying the file format version.  The letter A represents version 0, and so on.

  * An 8-character string field giving the file creation date in the format YYYYMMDD.

  * A 6-character string field giving the file creation time in the format HHMMSS.

Identification Records
======================

The product identification record has tag code 1.  It consists of a single string field giving the name of the product that wrote the portable file.

The subproduct identification record has tag code 3.  It consists of a single string field giving additional information on the product that wrote the portable file.

Variable Count Record
=====================

The variable count record has tag code 4.  It consists of two integer fields.  The first contains the number of variables in the file dictionary.  The purpose of the second is unknown; it contains the value 161 in all portable files examined so far.

Variable Records
================

Each variable record represents a single variable.  Variable records have tag code 7.  They have the following structure:

  * Width (integer).  This is 0 for a numeric variable, and a number between 1 and 255 for a string variable.

  * Name (string).  1--8 characters long.  Must be in all capitals.

  * Print format.  This is a set of three integer fields:

       - Format type (see Variable Record).

       - Format width.  1--40.

       - Number of decimal places.  1--40.

  * Write format.  Same structure as the print format described above.

Each variable record can optionally be followed by a missing value record, which has tag code 8.  A missing value record has one field, the missing value itself (a floating-point or string, as appropriate).  Up to three of these missing value records can be used.

There is also a record for missing value ranges, which has tag code B.  It is followed by two fields representing the range, which are floating-point or string as appropriate.  If a missing value range is present, it may be followed by a single missing value record.

Tag codes 9 and A represent LO THRU X and X THRU HI ranges, respectively.  Each is followed by a single field representing X.  If one of the ranges is present, it may be followed by a single missing value record.

In addition, each variable record can optionally be followed by a variable label record, which has tag code C.  A variable label record has one field, the variable label itself (string).

Value Label Records
===================

Value label records have tag code D.  They have the following format:

  * Variable count (integer).

  * List of variables (strings).  The variable count specifies the number in the list.  Variables are specified by their names.  All variables must be of the same type (numeric or string).

  * Label count (integer).

  * List of (value, label) tuples.  The label count specifies the number of tuples.  Each tuple consists of a value, which is numeric or string as appropriate to the variables, followed by a label (string).

Portable File Data
==================

The data record has tag code F.  There is only one tag for all the data; thus, all the data must follow the dictionary.  The data is terminated by the end-of-file marker Z, which is not valid as the beginning of a data element.

Data elements are output in the same order as the variable records describing them.  String variables are output as string fields, and numeric variables are output as floating-point fields.

q2c Input Format
****************

PSPP statistical procedures have a bizarre and somewhat irregular syntax.  Despite this, a parser generator has been written that adequately addresses many of the possibilities and tries to provide hooks for the exceptional cases.  This parser generator is named q2c.

Invoking q2c
============

     q2c INPUT.Q OUTPUT.C

q2c translates a .q file into a .c file.  It takes exactly two command-line arguments, which are the input file name and output file name, respectively.  q2c does not accept any command-line options.

q2c Input Structure
===================

q2c input files are divided into two sections: the grammar rules and the supporting code.  The grammar rules, which make up the first part of the input, are used to define the syntax of the statistical procedure to be parsed.  The supporting code, following the grammar rules, are copied largely unchanged to the output file, except for certain escapes.

The most important lines in the grammar rules are used for defining procedure syntax.  These lines can be prefixed with a dollar sign ($), which prevents Emacs' CC-mode from munging them.  Besides this, a bang (!) at the beginning of a line causes the line, minus the bang, to be written verbatim to the output file (useful for comments).  As a third special case, any line that begins with the exact characters /* *INDENT is ignored and not written to the output. This allows .q files to be processed through indent without being munged.

The syntax of the grammar rules themselves is given in the following sections.

The supporting code is passed into the output file largely unchanged. However, the following escapes are supported.  Each escape must appear on a line by itself.

/* (header) */

     Expands to a series of C #include directives which include the headers that are required for the parser generated by q2c.

/* (decls SCOPE) */

     Expands to C variable and data type declarations for the variables and enums input and output by the q2c parser.  SCOPE must be either local or global.  local causes the declarations to be output as function locals.  global causes them to be declared as static module variables; thus, global is a bit of a misnomer.

/* (parser) */

     Expands to the entire parser.  Must be enclosed within a C function.

/* (free) */

     Expands to a set of calls to the free function for variables declared by the parser.  Only needs to be invoked if subcommands of type string are used in the grammar rules.

Grammar Rules
=============

The grammar rules describe the format of the syntax that the parser generated by q2c will understand.  The way that the grammar rules are included in q2c input file are described above.

The grammar rules are divided into tokens of the following types:

Identifier (ID)

     An identifier token is a sequence of letters, digits, and underscores (_).  Identifiers are not case-sensitive.

String (STRING)

     String tokens are initiated by a double-quote character (") and consist of all the characters between that double quote and the next double quote, which must be on the same line as the first.  Within a string, a backslash can be used as a ``literal escape''.  The only reasons to use a literal escape are to include a double quote or a backslash within a string.

Special character

     Other characters, other than whitespace, constitute tokens in themselves.

The syntax of the grammar rules is as follows:

     grammar-rules ::= ID : subcommands .
     subcommands ::= subcommand
                 ::= subcommands ; subcommand

The syntax begins with an ID or STRING token that gives the name of the procedure to be parsed.  The rest of the syntax consists of subcommands separated by semicolons (;) and terminated with a full stop (.).

     subcommand ::= sbc-options ID sbc-defn
     sbc-options ::=
                 ::= sbc-option
                 ::= sbc-options sbc-options
     sbc-option ::= *
                ::= +
     sbc-defn ::= opt-prefix = specifiers
              ::= [ ID ] = array-sbc
              ::= opt-prefix = sbc-special-form
     opt-prefix ::=
                ::= ( ID )

Each subcommand can be prefixed with one or more option characters.  An asterisk (*) is used to indicate the default subcommand; the keyword used for the default subcommand can be omitted in the PSPP syntax file.  A plus sign (+) is used to indicate that a subcommand can appear more than once; if it is not present then that subcommand can appear no more than once.

The subcommand name appears after the option characters.

There are three forms of subcommands.  The first and most common form simply gives an equals sign (=) and a list of specifiers, which can each be set to a single setting.  The second form declares an array, which is a set of flags that can be individually turned on by the user. There are also several special forms that do not take a list of specifiers.

Arrays require an additional ID argument.  This is used as a prefix, prepended to the variable names constructed from the specifiers.  The other forms also allow an optional prefix to be specified.

     array-sbc ::= alternatives
               ::= array-sbc , alternatives
     alternatives ::= ID
                  ::= alternatives | ID

An array subcommand is a set of Boolean values that can independently be turned on by the user, listed separated by commas (,).  If an value has more than one name then these names are separated by pipes (|).

     specifiers ::= specifier
                ::= specifiers , specifier
     specifier ::= opt-id : settings
     opt-id ::=
            ::= ID

Ordinary subcommands (other than arrays and special forms) require a list of specifiers.  Each specifier has an optional name and a list of settings.  If the name is given then a correspondingly named variable will be used to store the user's choice of setting.  If no name is given then there is no way to tell which setting the user picked; in this case the settings should probably have values attached.

     settings ::= setting
              ::= settings / setting
     setting ::= setting-options ID setting-value
     setting-options ::=
                     ::= *
                     ::= !
                     ::= * !

Individual settings are separated by forward slashes (/).  Each setting can be as little as an ID token, but options and values can optionally be included.  The * option means that, for this setting, the ID can be omitted.  The ! option means that this option is the default for its specifier.

     setting-value ::=
                   ::= ( setting-value-2 )
                   ::= setting-value-2
     setting-value-2 ::= setting-value-options setting-value-type : ID
                         setting-value-restriction
     setting-value-options ::=
                           ::= *
     setting-value-type ::= N
                        ::= D
     setting-value-restriction ::=
                               ::= , STRING

Settings may have values.  If the value must be enclosed in parentheses, then enclose the value declaration in parentheses.  Declare the setting type as n or d for integer or floating point type, respectively.  The given ID is used to construct a variable name. If option * is given, then the value is optional; otherwise it must be specified whenever the corresponding setting is specified.  A ``restriction'' can also be specified which is a string giving a C expression limiting the valid range of the value.  The special escape %s should be used within the restriction to refer to the setting's value variable.

     sbc-special-form ::= VAR
                      ::= VARLIST varlist-options
                      ::= INTEGER opt-list
                      ::= DOUBLE opt-list
                      ::= PINT
                      ::= STRING (the literal word STRING) string-options
                      ::= CUSTOM
     varlist-options ::=
                     ::= ( STRING )
     opt-list ::=
              ::= LIST
     string-options ::=
                    ::= ( STRING STRING )

The special forms are of the following types:

VAR

     A single variable name.

VARLIST

     A list of variables.  If given, the string can be used to provide PV_* options to the call to parse_variables.

INTEGER

     A single integer value.

INTEGER LIST

     A list of integers separated by spaces or commas.

DOUBLE

     A single floating-point value.

DOUBLE LIST

     A list of floating-point values.

PINT

     A single positive integer value.

STRING

     A string value.  If the options are given then the first string is an expression giving a restriction on the value of the string; the second string is an error message to display when the restriction is violated.

CUSTOM

     A custom function is used to parse this subcommand.  The function must have prototype int custom_NAME (void).  It should return 0 on failure (when it has already issued an appropriate diagnostic), 1 on success, or 2 if it fails and the calling function should issue a syntax error on behalf of the custom handler.

Bugs
****

Known bugs
==========

This is the list of known bugs in PSPP.  In addition, see Not Implemented, and see Functions Not Implemented, for lists of bugs due to features not implemented.  For known bugs in individual language features, see the documentation for that feature.

  * Nothing has yet been tested exhaustively. Be cautious using PSPP to make important decisions.

  * make check fails on some systems that don't like the syntax.  I'm not sure why.  If someone could make an attempt to track this down, it would be appreciated.

  * PostScript driver bugs:

       - Does not support driver arguments `max-fonts-simult' or `optimize-text-size'.

       - Minor problems with font-encodings.

       - Fails to align fonts along their baselines.

       - Does not support certain bizarre line intersections--should never crop up in practice.

       - Does not gracefully substitute for existing fonts whose encodings are missing.

       - Does not perform italic correction or left italic correction on font changes.

       - Encapsulated PostScript is unimplemented.

  * ASCII driver bugs:

          Does not support `infinite length' or `infinite width' paper.

See below for information on reporting bugs not listed here.

Contacting the Author
=====================

The author can be contacted at e-mail address <blp@gnu.org>.

PSPP bug reports should be sent to <bug-gnu-pspp@gnu.org>.