SMISSING

[pspp] / doc / statistics.texi

diff --git a/doc/statistics.texi b/doc/statistics.texi
index 78b76bfbc492e2a1d48622ceb04f9bd629fd6e77..5b8b841933f3974b2f12410df414864a15b87523 100644 (file)
--- a/doc/statistics.texi
+++ b/doc/statistics.texi
@@ -1506,7 +1506,7 @@ order:
 
 @table @asis
 @item Explicit categories.
 
 @table @asis
 @item Explicit categories.

-@anchor{CTABLE Explicit Category List}
+@anchor{CTABLES Explicit Category List}

 To explicitly specify categories to include, list the categories
 within square brackets in the desired sort order.  Use spaces or
 commas to separate values.  Categories not covered by the list are
 To explicitly specify categories to include, list the categories
 within square brackets in the desired sort order.  Use spaces or
 commas to separate values.  Categories not covered by the list are


@@ -1707,9 +1707,46 @@ is optional.
 
 With @code{SMISSING=VARIABLE}, which is the default, missing values
 are excluded on a variable-by-variable basis.  With
 
 With @code{SMISSING=VARIABLE}, which is the default, missing values
 are excluded on a variable-by-variable basis.  With

-@code{SMISSING=LISTWISE}, when scalar variables are stacked, a missing
-value for any of the scalar variables causes the case to be excluded
-for all of them.
+@code{SMISSING=LISTWISE}, when stacked scalar variables are nested
+together with a categorical variable, a missing value for any of the
+scalar variables causes the case to be excluded for all of them.
+
+As an example, consider the following dataset, in which @samp{x} is a
+categorical variable and @samp{y} and @samp{z} are scale:
+
+@psppoutput{ctables18}
+
+@noindent
+With the default missing-value treatment, @samp{x}'s mean is 20, based
+on the values 10, 20, and 30, and @samp{y}'s mean is 50, based on 40,
+50, and 60:
+
+@example
+CTABLES /TABLE (y + z) > x.
+@end example
+@psppoutput{ctables19}
+
+@noindent
+By adding @code{SMISSING=LISTWISE}, only cases where @samp{y} and
+@samp{z} are both non-missing are considered, so @samp{x}'s mean
+becomes 15, as the average of 10 and 20, and @samp{y}'s mean becomes
+55, the average of 50 and 60:
+
+@example
+CTABLES /SMISSING LISTWISE /TABLE (y + z) > x.
+@end example
+@psppoutput{ctables20}
+
+@noindent
+Even with @code{SMISSING=LISTWISE}, if @samp{y} and @samp{z} are
+separately nested with @samp{x}, instead of using a single @samp{>}
+operator, missing values revert to being considered on a
+variable-by-variable basis:
+
+@example
+CTABLES /SMISSING LISTWISE /TABLE (y > x) + (z > x).
+@end example
+@psppoutput{ctables21}

 
 @node CTABLES Computed Categories
 @subsection Computed Categories
 
 @node CTABLES Computed Categories
 @subsection Computed Categories


@@ -1722,7 +1759,7 @@ for all of them.
 categories created using arithmetic on categories obtained from the
 data.  The @code{PCOMPUTE} subcommand defines computed categories,
 which can then be used in two places: on @code{CATEGORIES} within an
 categories created using arithmetic on categories obtained from the
 data.  The @code{PCOMPUTE} subcommand defines computed categories,
 which can then be used in two places: on @code{CATEGORIES} within an

-explicit category list (@pxref{CTABLE Explicit Category List}), and on
+explicit category list (@pxref{CTABLES Explicit Category List}), and on

 the @code{PPROPERTIES} subcommand to define further properties for a
 given postcompute.
 
 the @code{PPROPERTIES} subcommand to define further properties for a
 given postcompute.
 


@@ -1749,7 +1786,7 @@ postcompute must have the same form.
 @itemx MISSING
 @itemx OTHERNM
 These forms evaluate to the summary statistics for categories matching
 @itemx MISSING
 @itemx OTHERNM
 These forms evaluate to the summary statistics for categories matching

-the given syntax, as described in previous sections (@pxref{CTABLE
+the given syntax, as described in previous sections (@pxref{CTABLES

 Explicit Category List}).  If more than one category matches, their
 values are summed.
 
 Explicit Category List}).  If more than one category matches, their
 values are summed.