-@node Data Selection, Conditionals and Looping, Data Manipulation, Top
+@node Data Selection
@chapter Selecting data for analysis
This chapter documents PSPP commands that temporarily or permanently
@menu
* FILTER:: Exclude cases based on a variable.
* N OF CASES:: Limit the size of the active file.
-* PROCESS IF:: Temporarily excluding cases.
* SAMPLE:: Select a specified proportion of cases.
* SELECT IF:: Permanently delete selected cases.
* SPLIT FILE:: Do multiple analyses with one command.
* WEIGHT:: Weight cases by a variable.
@end menu
-@node FILTER, N OF CASES, Data Selection, Data Selection
+@node FILTER
@section FILTER
@vindex FILTER
OFF}. However, if @cmd{FILTER} is placed after TEMPORARY, it filters only
the next procedure or procedure-like command.
-@node N OF CASES, PROCESS IF, FILTER, Data Selection
+@node N OF CASES
@section N OF CASES
@vindex N OF CASES
N [OF CASES] num_of_cases [ESTIMATED].
@end display
-Sometimes you may want to disregard cases of your input. @cmd{N} can
-do this. @code{N 100} tells PSPP to disregard all cases after the
-first 100.
-
-If the value specified for @cmd{N} is greater than the number of cases
-read in, the value is ignored.
-
-@cmd{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 @cmd{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 @cmd{N} is executed
-@emph{do} cause cases to be discarded.
-
-@cmd{SAMPLE}, @cmd{PROCESS IF}, and @cmd{SELECT IF} have
-precedence over @cmd{N}---the same results are obtained by both of the
-following fragments, given the same random number seeds:
-
-@example
-@i{@dots{}set up, read in data@dots{}}
-N 100.
-SAMPLE .5.
-@i{@dots{}analyze data@dots{}}
-
-@i{@dots{}set up, read in data@dots{}}
-SAMPLE .5.
-N 100.
-@i{@dots{}analyze data@dots{}}
-@end example
-
-Both fragments above first randomly sample approximately half of the
-cases, then select the first 100 of those sampled.
-
-@cmd{N} with the @code{ESTIMATED} keyword gives an
-estimated number of cases before @cmd{DATA LIST} or another command to
-read in data. @code{ESTIMATED} never limits the number of cases
-processed by procedures. PSPP currently does not make use of
-case count estimates.
-
-When @cmd{N} is specified after @cmd{TEMPORARY}, it affects only
-the next procedure (@pxref{TEMPORARY}).
-
-@node PROCESS IF, SAMPLE, N OF CASES, Data Selection
-@section PROCESS IF
-@vindex PROCESS IF
-
-@example
-PROCESS IF expression.
-@end example
-
-@cmd{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 (@pxref{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, @cmd{PROCESS IF}
-always takes effect immediately before data passes to the procedure.
-Only one @cmd{PROCESS IF} command may be in effect at any given time.
-
-The effects of @cmd{PROCESS IF} are similar, but not identical, to the
-effects of executing @cmd{TEMPORARY}, then @cmd{SELECT IF}
-(@pxref{SELECT IF}).
-
-The filtering performed by @cmd{PROCESS IF} takes place immediately
-before cases pass to a procedure for analysis. Because @cmd{PROCESS
-IF} affects only a single procedure, its placement relative to
-@cmd{TEMPORARY} is unimportant.
-
-@cmd{PROCESS IF} is deprecated. It is included for compatibility with
-old command files. New syntax files should use @cmd{SELECT IF} or
-@cmd{FILTER} instead.
-
-@node SAMPLE, SELECT IF, PROCESS IF, Data Selection
+@cmd{N OF CASES} limits the number of cases processed by any
+procedures that follow it in the command stream. @code{N OF CASES
+100}, for example, tells PSPP to disregard all cases after the first
+100.
+
+When @cmd{N OF CASES} is specified after @cmd{TEMPORARY}, it affects
+only the next procedure (@pxref{TEMPORARY}). Otherwise, cases beyond
+the limit specified are not processed by any later procedure.
+
+If the limit specified on @cmd{N OF CASES} is greater than the number
+of cases in the active file, it has no effect.
+
+When @cmd{N OF CASES} is used along with @cmd{SAMPLE} or @cmd{SELECT
+IF}, the case limit is applied to the cases obtained after sampling or
+case selection, regardless of how @cmd{N OF CASES} is placed relative
+to @cmd{SAMPLE} or @cmd{SELECT IF} in the command file. Thus, the
+commands @code{N OF CASES 100} and @code{SAMPLE .5} will both randomly
+sample approximately half of the active file's cases, then select the
+first 100 of those sampled, regardless of their order in the command
+file.
+
+@cmd{N OF CASES} with the @code{ESTIMATED} keyword gives an estimated
+number of cases before @cmd{DATA LIST} or another command to read in
+data. @code{ESTIMATED} never limits the number of cases processed by
+procedures. PSPP currently does not make use of case count estimates.
+
+@node SAMPLE
@section SAMPLE
@vindex SAMPLE
differing endianness or floating-point formats. By default, the
random number seed is based on the system time.
-@node SELECT IF, SPLIT FILE, SAMPLE, Data Selection
+@node SELECT IF
@section SELECT IF
@vindex SELECT IF
(@pxref{TEMPORARY}), the @cmd{LAG} function may not be used
(@pxref{LAG}).
-@node SPLIT FILE, TEMPORARY, SELECT IF, Data Selection
+@node SPLIT FILE
@section SPLIT FILE
@vindex SPLIT FILE
@display
-Two possible syntaxes:
- SPLIT FILE BY var_list.
- SPLIT FILE OFF.
+SPLIT FILE [@{LAYERED, SEPARATE@}] BY var_list.
+SPLIT FILE OFF.
@end display
@cmd{SPLIT FILE} allows multiple sets of data present in one data
An independent analysis is carried out for each group of cases, and the
variable values for the group are printed along with the analysis.
+When a list of variable names is specified, one of the keywords
+LAYERED or SEPARATE may also be specified. If provided, either
+keyword are ignored.
+
Groups are formed only by @emph{adjacent} cases. To create a split
using a variable where like values are not adjacent in the working file,
you should first sort the data by that variable (@pxref{SORT CASES}).
When @cmd{SPLIT FILE} is specified after @cmd{TEMPORARY}, it affects only
the next procedure (@pxref{TEMPORARY}).
-@node TEMPORARY, WEIGHT, SPLIT FILE, Data Selection
+@node TEMPORARY
@section TEMPORARY
@vindex TEMPORARY
10.5, 13, 15. The data read by the first @cmd{DESCRIPTIVES} are 1, 2,
5, 7.5, 10, 12.
-@node WEIGHT, , TEMPORARY, Data Selection
+@node WEIGHT
@section WEIGHT
@vindex WEIGHT
@cmd{WEIGHT} does not cause cases in the active file to be replicated in
memory.
-@setfilename ignored
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