docs

[pspp] / doc / combining.texi

diff --git a/doc/combining.texi b/doc/combining.texi
index 00f6067a98aa7b2967d62e2e86806c654db1cbab..a237c1a5bded14506120ad10b18df53e6a686bf8 100644 (file)
--- a/doc/combining.texi
+++ b/doc/combining.texi
@@ -1,3 +1,12 @@
+@c PSPP - a program for statistical analysis.
+@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;
+@c with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+@c A copy of the license is included in the section entitled "GNU
+@c Free Documentation License".
+@c
 @node Combining Data Files
 @chapter Combining Data Files
 
@@ -58,9 +67,11 @@ This section describes the syntactical features in common among the
 @cmd{ADD FILES}, @cmd{MATCH FILES}, and @cmd{UPDATE} commands.  The
 following sections describe details specific to each command.
 
-Each of these commands reads two or more input files and combines
-them.  The command's output becomes the new active dataset.  The input
-files are not changed on disk.
+Each of these commands reads two or more input files and combines them.
+The command's output becomes the new active dataset.
+None of the commands actually change the input files.
+Therefore, if you want the changes to become permanent, you must explicitly
+save them using an appropriate procedure or transformation (@pxref{System and Portable File IO}).
 
 The syntax of each command begins with a specification of the files to
 be read as input.  For each input file, specify FILE with a system
@@ -77,7 +88,7 @@ Each @subcmd{FILE} subcommand may be followed by any number of @subcmd{RENAME}
 subcommands that specify a parenthesized group or groups of variable
 names as they appear in the input file, followed by those variables'
 new names, separated by an equals sign (@subcmd{=}),
-e.g. @subcmd{/RENAME=(OLD1=NEW1)(OLD2=NEW2)}.  To rename a single
+@i{e.g.} @subcmd{/RENAME=(OLD1=NEW1)(OLD2=NEW2)}.  To rename a single
 variable, the parentheses may be omitted: @subcmd{/RENAME=@var{old}=@var{new}}.
 Within a parenthesized group, variables are renamed simultaneously, so
 that @subcmd{/RENAME=(@var{A} @var{B}=@var{B} @var{A})} exchanges the
@@ -117,7 +128,7 @@ similarly for value labels and missing values.
 
 @item
 The file label of the new active dataset (@pxref{FILE LABEL}) is that of the
-first specified FILE that has a file label.
+first specified @subcmd{FILE} that has a file label.
 
 @item
 The documents in the new active dataset (@pxref{DOCUMENT}) are the
@@ -132,7 +143,7 @@ active dataset is not weighted.
 
 The remaining subcommands apply to the output file as a whole, rather
 than to individual input files.  They must be specified at the end of
-the command specification, following all of the FILE and related
+the command specification, following all of the @subcmd{FILE} and related
 subcommands.  The most important of these subcommands is @subcmd{BY}, which
 specifies a set of one or more variables that may be used to find
 corresponding cases in each of the input files.  The variables
@@ -168,6 +179,9 @@ only in files that are not present for the current case are set to the
 system-missing value for numeric variables or spaces for string
 variables.
 
+These commands may combine any number of files, limited only by the
+machine's memory.
+
 @node ADD FILES
 @section ADD FILES
 @vindex ADD FILES
@@ -250,7 +264,7 @@ to cases output after their input has been exhausted.
 
 @item
 If @subcmd{BY} is used, @cmd{MATCH FILES} combines cases from each input file that
-have identical values for the BY variables.
+have identical values for the @subcmd{BY} variables.
 
 When @subcmd{BY} is used, @subcmd{TABLE} subcommands may be used to introduce @dfn{table
 lookup file}.  @subcmd{TABLE} has same syntax as @subcmd{FILE}, and the @subcmd{RENAME}, @subcmd{IN}, and
@@ -296,7 +310,7 @@ Once per command:
 @end display
 
 @cmd{UPDATE} updates a @dfn{master file} by applying modifications
-from one or more @dfn{transaction files}.  
+from one or more @dfn{transaction files}.
 
 @cmd{UPDATE} shares the bulk of its syntax with other @pspp{} commands for
 combining multiple data files.  @xref{Combining Files Common Syntax},
@@ -315,14 +329,14 @@ case in the master file:
 @itemize @bullet
 @item
 When a match is found, then the values of the variables present in the
-transaction file replace those variable's values in the new active
+transaction file replace those variables' values in the new active
 file.  If there are matching cases in more than more transaction file,
 @pspp{} applies the replacements from the first transaction file, then
 from the second transaction file, and so on.  Similarly, if a single
 transaction file has cases with duplicate @subcmd{BY} values, then those are
 applied in order to the master file.
 
-When a variable in a transaction file has a missing value or a string
+When a variable in a transaction file has a missing value or when a string
 variable's value is all blanks, that value is never used to update the
 master file.