-@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
-select data records from the active file for analysis.
+This chapter documents @pspp{} commands that temporarily or permanently
+select data records from the active dataset for analysis.
@menu
* FILTER:: Exclude cases based on a variable.
-* N OF CASES:: Limit the size of the active file.
-* PROCESS IF:: Temporarily excluding cases.
+* N OF CASES:: Limit the size of the active dataset.
* 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
@display
-FILTER BY var_name.
+FILTER BY @var{var_name}.
FILTER OFF.
@end display
@cmd{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
+To set up filtering, specify @subcmd{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.
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 @code{FILTER
-OFF}. However, if @cmd{FILTER} is placed after TEMPORARY, it filters only
+OFF}. However, if @cmd{FILTER} is placed after @cmd{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
@display
-N [OF CASES] num_of_cases [ESTIMATED].
+N [OF CASES] @var{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 dataset, 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 dataset'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
@display
-SAMPLE num1 [FROM num2].
+SAMPLE @var{num1} [FROM @var{num2}].
@end display
@cmd{SAMPLE} randomly samples a proportion of the cases in the active
file. Unless it follows @cmd{TEMPORARY}, it operates as a
-transformation, permanently removing cases from the active file.
+transformation, permanently removing cases from the active dataset.
The proportion to sample can be expressed as a single number between 0
-and 1. If @code{k} is the number specified, and @code{N} is the number
-of currently-selected cases in the active file, then after
-@code{SAMPLE @var{k}.}, approximately @code{k*N} cases will be
+and 1. If @var{k} is the number specified, and @var{N} is the number
+of currently-selected cases in the active dataset, then after
+@subcmd{SAMPLE @var{k}.}, approximately @var{k}*@var{N} cases will be
selected.
-The proportion to sample can also be specified in the style @code{SAMPLE
+The proportion to sample can also be specified in the style @subcmd{SAMPLE
@var{m} FROM @var{N}}. With this style, cases are selected as follows:
@enumerate
@item
If @var{N} is equal to the number of currently-selected cases in the
-active file, exactly @var{m} cases will be selected.
+active dataset, exactly @var{m} cases will be selected.
@item
If @var{N} is greater than the number of currently-selected cases in the
-active file, an equivalent proportion of cases will be selected.
+active dataset, an equivalent proportion of cases will be selected.
@item
If @var{N} is less than the number of currently-selected cases in the
active, exactly @var{m} cases will be selected @emph{from the first
-@var{N} cases in the active file.}
+@var{N} cases in the active dataset.}
@end enumerate
@cmd{SAMPLE} and @cmd{SELECT IF} are performed in
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
@display
-SELECT IF expression.
+SELECT IF @var{expression}.
@end display
-@cmd{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 @cmd{TEMPORARY} is in effect
+@cmd{SELECT IF} selects cases for analysis based on the value of
+@var{expression}. Cases not selected are permanently eliminated
+from the active dataset, unless @cmd{TEMPORARY} is in effect
(@pxref{TEMPORARY}).
Specify a boolean expression (@pxref{Expressions}). If the value of the
(@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{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
+@subcmd{LAYERED} or @subcmd{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}).
-Specify OFF to disable @cmd{SPLIT FILE} and resume analysis of the
-entire active file as a single group of data.
+Specify @subcmd{OFF} to disable @cmd{SPLIT FILE} and resume analysis of the
+entire active dataset as a single group of data.
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
@cmd{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.
+command. Their effects will not be saved to the active dataset.
The only specification on @cmd{TEMPORARY} is the command name.
20
24
END DATA.
+
COMPUTE X=X/2.
+
TEMPORARY.
COMPUTE X=X+3.
+
DESCRIPTIVES X.
DESCRIPTIVES X.
@end example
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
@display
-WEIGHT BY var_name.
+WEIGHT BY @var{var_name}.
WEIGHT OFF.
@end display
@cmd{WEIGHT} assigns cases varying weights,
-changing the frequency distribution of the active file. Execution of
+changing the frequency distribution of the active dataset. Execution of
@cmd{WEIGHT} is delayed until data have been read.
If a variable name is specified, @cmd{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
+procedures. Use of keyword @subcmd{BY} is optional but recommended. Weighting
variables must be numeric. Scratch variables may not be used for
weighting (@pxref{Scratch Variables}).
-When OFF is specified, subsequent statistical procedures will weight all
+When @subcmd{OFF} is specified, subsequent statistical procedures will weight all
cases equally.
A positive integer weighting factor @var{w} on a case will yield the
When @cmd{WEIGHT} is specified after @cmd{TEMPORARY}, it affects only
the next procedure (@pxref{TEMPORARY}).
-@cmd{WEIGHT} does not cause cases in the active file to be replicated in
-memory.
-@setfilename ignored
+@cmd{WEIGHT} does not cause cases in the active dataset to be
+replicated in memory.
projects / pspp / blobdiff