X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fcombining.texi;h=93f4e82c985fe4a777325b077ca9d319fd37c8e0;hb=refs%2Fheads%2Fpivot-table2;hp=00f6067a98aa7b2967d62e2e86806c654db1cbab;hpb=1b1837591924226078c96db15888b68beec2ef6d;p=pspp diff --git a/doc/combining.texi b/doc/combining.texi index 00f6067a98..93f4e82c98 100644 --- a/doc/combining.texi +++ b/doc/combining.texi @@ -58,9 +58,11 @@ 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 @@ -117,7 +119,7 @@ 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 +134,7 @@ 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 @@ -250,7 +252,7 @@ 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 @@ -315,14 +317,14 @@ 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.