@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 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
@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,
@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.
@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).
projects / pspp / blobdiff