@c PSPP - a program for statistical analysis.
-@c Copyright (C) 2017 Free Software Foundation, Inc.
+@c Copyright (C) 2017, 2020 Free Software Foundation, Inc.
@c Permission is granted to copy, distribute and/or modify this document
@c under the terms of the GNU Free Documentation License, Version 1.3
@c or any later version published by the Free Software Foundation;
@cindex @pspp{}, language
This chapter discusses elements common to many @pspp{} commands.
-Later chapters will describe individual commands in detail.
+Later chapters describe individual commands in detail.
@menu
* Tokens:: Characters combine to form tokens.
No white space is allowed within a number token, except for horizontal
white space between @samp{-} and the rest of the number.
-The last example above, @samp{8945.} will be interpreted as two
+The last example above, @samp{8945.} is interpreted as two
tokens, @samp{8945} and @samp{.}, if it is the last token on a line.
@xref{Commands, , Forming commands of tokens}.
@cindex case-sensitivity
Strings are literal sequences of characters enclosed in pairs of
single quotes (@samp{'}) or double quotes (@samp{"}). To include the
-character used for quoting in the string, double it, e.g.@:
+character used for quoting in the string, double it, @i{e.g.}@:
@samp{'it''s an apostrophe'}. White space and case of letters are
significant inside strings.
punctuator only as the last character on a line (except white space).
When it is the last non-space character on a line, a period is not
treated as part of another token, even if it would otherwise be part
-of, e.g.@:, an identifier or a floating-point number.
+of, @i{e.g.}@:, an identifier or a floating-point number.
@end table
@node Commands
@item Transformations
@cindex transformations
Perform operations on data and write data to output files. Transformations
-are not carried out until a procedure is executed.
+are not carried out until a procedure is executed.
@item Restricted transformations
@cindex restricted transformations
Valid in any state.
@item
When executed in the initial or procedure state, causes a transition to
-the transformation state.
+the transformation state.
@item
Clears the active dataset if executed in the procedure or transformation
state.
@item
Invalid in input-program and file-type states.
@item
-Causes a transition to the intput-program state.
+Causes a transition to the intput-program state.
@item
Clears the active dataset.
@end itemize
@cindex variable names, ending with period
The final character in a variable name should not be @samp{.}, because
such an identifier will be misinterpreted when it is the final token
-on a line: @code{FOO.} will be divided into two separate tokens,
+on a line: @code{FOO.} is divided into two separate tokens,
@samp{FOO} and @samp{.}, indicating end-of-command. @xref{Tokens}.
@cindex @samp{_}
Similar to print format, but used by the @cmd{WRITE} command
(@pxref{WRITE}).
+@cindex measurement level
+@item Measurement level
+One of the following:
+
+@table @asis
+@item Nominal
+Each value of a nominal variable represents a distinct category. The
+possible categories are finite and often have value labels. The order
+of categories is not significant. Political parties, US states, and
+yes/no choices are nominal. Numeric and string variables can be
+nominal.
+
+@item Ordinal
+Ordinal variables also represent distinct categories, but their values
+are arranged according to some natural order. Likert scales, e.g.@:
+from strongly disagree to strongly agree, are ordinal. Data grouped
+into ranges, e.g.@: age groups or income groups, are ordinal. Both
+numeric and string variables can be ordinal. String values are
+ordered alphabetically, so letter grades from A to F will work as
+expected, but @code{poor}, @code{satisfactory}, @code{excellent} will
+not.
+
+@item Scale
+Scale variables are ones for which differences and ratios are
+meaningful. These are often values which have a natural unit
+attached, such as age in years, income in dollars, or distance in
+miles. Only numeric variables are scalar.
+@end table
+
@cindex custom attributes
@item Custom attributes
User-defined associations between names and values. @xref{VARIABLE
@cindex @code{$DATE}
@item $DATE
Date the @pspp{} process was started, in format A9, following the
-pattern @code{DD MMM YY}.
+pattern @code{DD-MMM-YY}.
+
+@cindex @code{$DATE11}
+@item $DATE11
+Date the @pspp{} process was started, in format A11, following the
+pattern @code{DD-MMM-YYYY}.
@cindex @code{$JDATE}
@item $JDATE
most of the time, the distinction between print and write formats is
unimportant.
-Input and output formats are specified to @pspp{} with
+Input and output formats are specified to @pspp{} with
a @dfn{format specification} of the
form @subcmd{@var{TYPE}@var{w}} or @code{TYPE@var{w}.@var{d}}, where
@var{TYPE} is one of the format types described later, @var{w} is a
by @pspp{}.
@menu
-* Basic Numeric Formats::
-* Custom Currency Formats::
-* Legacy Numeric Formats::
-* Binary and Hexadecimal Numeric Formats::
-* Time and Date Formats::
-* Date Component Formats::
-* String Formats::
+* Basic Numeric Formats::
+* Custom Currency Formats::
+* Legacy Numeric Formats::
+* Binary and Hexadecimal Numeric Formats::
+* Time and Date Formats::
+* Date Component Formats::
+* String Formats::
@end menu
@node Basic Numeric Formats
@samp{+} or @samp{-} and exactly three digits. Numbers with magnitude
less than 10**-999 or larger than 10**999 are not supported by most
computers, but if they are supported then their output is considered
-to overflow the field and will be output as asterisks.
+to overflow the field and they are output as asterisks.
@item
On most computers, no more than 15 decimal digits are significant in
Special values such as infinities and ``not a number'' values are
usually converted to the system-missing value before printing. In a few
circumstances, these values are output directly. In fields of width 3
-or greater, special values are output as however many characters will
+or greater, special values are output as however many characters
fit from @code{+Infinity} or @code{-Infinity} for infinities, from
@code{NaN} for ``not a number,'' or from @code{Unknown} for other values
(if any are supported by the system). In fields under 3 columns wide,
@display
SET CC@var{x}=@t{"}@var{string}@t{"}.
@end display
-@noindent
+@noindent
where @var{x} is A, B, C, D, or E, and @var{string} is no more than 16
characters long.
@var{string} must contain exactly three commas or exactly three periods
(but not both), except that a single quote character may be used to
``escape'' a following comma, period, or single quote. If three commas
-are used, commas will be used for grouping in output, and a period will
-be used as the decimal point. Uses of periods reverses these roles.
+are used, commas are used for grouping in output, and a period
+is used as the decimal point. Uses of periods reverses these roles.
The commas or periods divide @var{string} into four fields, called the
@dfn{negative prefix}, @dfn{prefix}, @dfn{suffix}, and @dfn{negative
The recommended field width depends on the floating-point format.
NATIVE (the default format), IDL, IDB, VD, VG, and ZL formats should use
a field width of 8. ISL, ISB, VF, and ZS formats should use a field
-width of 4. Other field widths will not produce useful results. The
+width of 4. Other field widths do not produce useful results. The
maximum field width is 8. No decimal places may be specified.
The default output format is F8.2.
@float
@multitable {DATETIME} {Min. Input Width} {Min. Output Width} {4-digit year}
-@headitem Format @tab Min. Input Width @tab Min. Output Width @tab Option
+@headitem Format @tab Min. Input Width @tab Min. Output Width @tab Option
@item DATE @tab 8 @tab 9 @tab 4-digit year
@item ADATE @tab 8 @tab 8 @tab 4-digit year
@item EDATE @tab 8 @tab 8 @tab 4-digit year
@item DTIME @tab 8 @tab 8 @tab seconds
@end multitable
@end float
-@noindent
+@noindent
In the table, ``Option'' describes what increased output width enables:
@table @asis
@item 4-digit year
-A field 2 columns wider than minimum will include a 4-digit year.
+A field 2 columns wider than the minimum includes a 4-digit year.
(DATETIME and YMDHMS formats always include a 4-digit year.)
@item seconds
-A field 3 columns wider than minimum will include seconds as well as
+A field 3 columns wider than the minimum includes seconds as well as
minutes. A field 5 columns wider than minimum, or more, can also
include a decimal point and fractional seconds (but no more than allowed
by the format's decimal places).
the field.
When a time or date exceeds the field width, characters are trimmed from
-the end until it fits. This can occur in an unusual situation, e.g.@:
+the end until it fits. This can occur in an unusual situation, @i{e.g.}@:
with a year greater than 9999 (which adds an extra digit), or for a
negative value on MTIME, TIME, or DTIME (which adds a leading minus sign).
@c What about out-of-range values?
The system-missing value is output as a period at the right end of the
-field.
+field.
@node Date Component Formats
@subsubsection Date Component Formats
However, sometimes it's useful to have a variable that keeps its value
between cases. You can do this with @cmd{LEAVE} (@pxref{LEAVE}), or you can
use a @dfn{scratch variable}. Scratch variables are variables whose
-names begin with an octothorpe (@samp{#}).
+names begin with an octothorpe (@samp{#}).
Scratch variables have the same properties as variables left with
@cmd{LEAVE}: they retain their values between cases, and for the first
@section File Handles
@cindex file handles
-A @dfn{file handle} is a reference to a data file, system file, or
+A @dfn{file handle} is a reference to a data file, system file, or
portable file. Most often, a file handle is specified as the
name of a file as a string, that is, enclosed within @samp{'} or
@samp{"}.
A file name string that begins or ends with @samp{|} is treated as the
name of a command to pipe data to or from. You can use this feature
to read data over the network using a program such as @samp{curl}
-(e.g.@: @code{GET '|curl -s -S http://example.com/mydata.sav'}), to
+(@i{e.g.}@: @code{GET '|curl -s -S http://example.com/mydata.sav'}), to
read compressed data from a file using a program such as @samp{zcat}
-(e.g.@: @code{GET '|zcat mydata.sav.gz'}), and for many other
+(@i{e.g.}@: @code{GET '|zcat mydata.sav.gz'}), and for many other
purposes.
@pspp{} also supports declaring named file handles with the @cmd{FILE
In some circumstances, @pspp{} must distinguish whether a file handle
refers to a system file or a portable file. When this is necessary to
-read a file, e.g.@: as an input file for @cmd{GET} or @cmd{MATCH FILES},
+read a file, @i{e.g.}@: as an input file for @cmd{GET} or @cmd{MATCH FILES},
@pspp{} uses the file's contents to decide. In the context of writing a
-file, e.g.@: as an output file for @cmd{SAVE} or @cmd{AGGREGATE}, @pspp{}
+file, @i{e.g.}@: as an output file for @cmd{SAVE} or @cmd{AGGREGATE}, @pspp{}
decides based on the file's name: if it ends in @samp{.por} (with any
capitalization), then @pspp{} writes a portable file; otherwise, @pspp{}
writes a system file.
@cindex @code{.}
@item @code{.}
The end of the command. This is not necessarily an actual dot in the
-syntax file: @xref{Commands}, for more details.
+syntax file (@pxref{Commands}).
@end table
@item
projects / pspp / blobdiff