AUTORECODE: Fix treatment of missing values.

[pspp] / doc / transformation.texi

diff --git a/doc/transformation.texi b/doc/transformation.texi
index e10cf8374fc16c4a37810c976568b91b5e950e37..5ee7febef0f78d79fc5f12c9d9ac8fc5e200041e 100644 (file)
--- a/doc/transformation.texi
+++ b/doc/transformation.texi
@@ -247,17 +247,33 @@ variables, @subcmd{INTO}, and a list of target variables.  There must the same
 number of source and target variables.  The target variables must not
 already exist.
 
 number of source and target variables.  The target variables must not
 already exist.
 

-By default, increasing values of a source variable (for a string, this
-is based on character code comparisons) are recoded to increasing values
-of its target variable.  To cause increasing values of a source variable
-to be recoded to decreasing values of its target variable (@var{n} down
-to 1), specify @subcmd{DESCENDING}.
+@cmd{AUTORECODE} ordinarily assigns each increasing non-missing value
+of a source variable (for a string, this is based on character code
+comparisons) to consecutive values of its target variable.  For
+example, the smallest non-missing value of the source variable is
+recoded to value 1, the next smallest to 2, and so on.  If the source
+variable has user-missing values, they are recoded to
+consecutive values just above the non-missing values.  For example, if
+a source variables has seven distinct non-missing values, then the
+smallest missing value would be recoded to 8, the next smallest to 9,
+and so on.
+
+Use @subcmd{DESCENDING} to reverse the sort order for non-missing
+values, so that the largest non-missing value is recoded to 1, the
+second-largest to 2, and so on.  Even with @subcmd{DESCENDING},
+user-missing values are still recoded in ascending order just above
+the non-missing values.
+
+The system-missing value is always recoded into the system-missing
+variable in target variables.

 
 @subcmd{PRINT} is currently ignored.
 
 The @subcmd{GROUP} subcommand is relevant only if more than one variable is to be
 recoded.   It causes a single mapping between source and target values to
 
 @subcmd{PRINT} is currently ignored.
 
 The @subcmd{GROUP} subcommand is relevant only if more than one variable is to be
 recoded.   It causes a single mapping between source and target values to

-be used, instead of one map per variable.
+be used, instead of one map per variable.  With @subcmd{GROUP},
+user-missing values are taken from the first source variable that has
+any user-missing values.

 
 If @subcmd{/BLANK=MISSING} is given, then string variables which contain only 
 whitespace are recoded as SYSMIS.  If @subcmd{/BLANK=VALID} is given then they
 
 If @subcmd{/BLANK=MISSING} is given, then string variables which contain only 
 whitespace are recoded as SYSMIS.  If @subcmd{/BLANK=VALID} is given then they