X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fdata-selection.texi;h=04269f32413733af6d626c3320b3142755264912;hb=163b1639eab9b48eab64752205d75f951547b5c7;hp=d7f4c79fc11d756c2fdbe278a10c0edb1862d62a;hpb=38006c9843177b65a2ce9bee47c1a8eeb6243973;p=pspp-builds.git

diff --git a/doc/data-selection.texi b/doc/data-selection.texi
index d7f4c79f..04269f32 100644
--- a/doc/data-selection.texi
+++ b/doc/data-selection.texi
@@ -1,4 +1,4 @@
-@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
@@ -14,7 +14,7 @@ select data records from the active file for analysis.
 * WEIGHT::                      Weight cases by a variable.
 @end menu
 
-@node FILTER, N OF CASES, Data Selection, Data Selection
+@node FILTER
 @section FILTER
 @vindex FILTER
 
@@ -51,51 +51,31 @@ the next procedure or procedure-like command.
 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.
+@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.
 
-If the value specified for @cmd{N} is greater than the number of cases
-read in, the value is ignored.
+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.
 
-@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.
+If the limit specified on @cmd{N OF CASES} is greater than the number
+of cases in the active file, it has no effect.
 
-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.)
+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.
 
-Transformation procedures performed after @cmd{N} is executed
-@emph{do} cause cases to be discarded.
-
-@cmd{SAMPLE} 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}).
+@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
@@ -146,7 +126,7 @@ 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.
 
-@node SELECT IF, SPLIT FILE, SAMPLE, Data Selection
+@node SELECT IF
 @section SELECT IF
 @vindex SELECT IF
 
@@ -172,7 +152,7 @@ When @cmd{SELECT IF} is specified following @cmd{TEMPORARY}
 (@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
 
@@ -205,7 +185,7 @@ entire active file 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
 
@@ -249,7 +229,7 @@ The data read by the first @cmd{DESCRIPTIVES} are 4, 5, 8,
 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
 
@@ -284,4 +264,3 @@ the next procedure (@pxref{TEMPORARY}).
 
 @cmd{WEIGHT} does not cause cases in the active file to be replicated in
 memory.
-@setfilename ignored