[Pspp-cvs] pspp/doc data-selection.texi

[Ben Pfaff]

CVSROOT:        /cvsroot/pspp
Module name:    pspp
Changes by:     Ben Pfaff <blp> 07/07/10 13:17:59

Modified files:
        doc            : data-selection.texi 

Log message:
        Improve N OF CASES documentation.

CVSWeb URLs:
http://cvs.savannah.gnu.org/viewcvs/pspp/doc/data-selection.texi?cvsroot=pspp&r1=1.6&r2=1.7

Patches:
Index: data-selection.texi
===================================================================
RCS file: /cvsroot/pspp/pspp/doc/data-selection.texi,v
retrieving revision 1.6
retrieving revision 1.7
diff -u -b -r1.6 -r1.7
--- data-selection.texi 6 Jun 2007 05:17:48 -0000       1.6
+++ data-selection.texi 10 Jul 2007 13:17:59 -0000      1.7
@@ -51,51 +51,31 @@
 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.
-
address@hidden 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
address@hidden cause cases to be discarded.
-
address@hidden 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:
-
address@hidden
address@hidden@dots{}set up, read in address@hidden
-N 100.
-SAMPLE .5.
address@hidden@dots{}analyze address@hidden
-
address@hidden@dots{}set up, read in address@hidden  
-SAMPLE .5.
-N 100.
address@hidden@dots{}analyze address@hidden
address@hidden example
-
-Both fragments above first randomly sample approximately half of the
-cases, then select the first 100 of those sampled.
-
address@hidden 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}).
address@hidden 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.
+
address@hidden 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