+The @code{TABLE} subcommand on @code{CTABLES} specifies two different
+kinds of variables: variables that divide tables into cells (which are
+always categorical) and variables being summarized (which may be
+categorical or scale). @pspp{} treats missing values differently in
+each kind of variable:
+
+@itemize @bullet
+@item
+For variables that divide tables into cells, per-variable category
+options determine which data is analyzed. If any of the categories
+for such a variable would exclude a case, then that case is not
+included.
+
+@item
+The treatment of missing values in variables being summarized varies
+between scale and scale and categorical variables. The following
+section describes their treatment in detail.
+
+By default, each summarized variable is considered separately for
+missing value treatment. A section below describes how to consider
+missing values listwise for summarizing scale variables.
+@end itemize
+
+@c TODO example
+
+@node CTABLES Missing Values for Summary Variables
+@subsubsection Missing Values for Summary Variables
+
+For summary variables, values that are valid and in included
+categories are analyzed, and values that are missing or in excluded
+categories are not analyzed, with the following exceptions:
+
+@itemize @bullet
+@item
+The ``@t{VALIDN}'' summary functions (@code{VALIDN}, @code{EVALIDN},
+@code{UVALIDN}, @code{@i{area}PCT.VALIDN}, and
+@code{U@i{area}PCT.VALIDN}) only count valid values in included
+categories (not missing values in included categories).
+
+@item
+The ``@t{TOTALN}'' summary functions (@code{TOTALN}, @code{ETOTALN},
+@code{UTOTALN}, @code{@i{area}PCT.TOTALN}), and
+@code{U@i{area}PCT.TOTALN} count all values (valid and missing) in
+included categories and missing (but not valid) values in excluded
+categories.
+@end itemize
+
+@noindent
+For categorical variables, system-missing values are never in included
+categories. For scale variables, there is no notion of included and
+excluded categories, so all values are effectively included.
+
+The following table provides another view of the above rules:
+
+@multitable {@w{ }@w{ }@w{ }@w{ }Missing values in excluded categories} {@t{VALIDN}} {other} {@t{TOTALN}}
+@headitem @tab @t{VALIDN} @tab other @tab @t{TOTALN}
+@item @headitemfont{Categorical variables:}
+@item @w{ }@w{ }@w{ }@w{ }Valid values in included categories @tab yes @tab yes @tab yes
+@item @w{ }@w{ }@w{ }@w{ }Missing values in included categories @tab --- @tab yes @tab yes
+@item @w{ }@w{ }@w{ }@w{ }Missing values in excluded categories @tab --- @tab --- @tab yes
+@item @w{ }@w{ }@w{ }@w{ }Valid values in excluded categories @tab --- @tab --- @tab ---
+@item @headitemfont{Scale variables:}
+@item @w{ }@w{ }@w{ }@w{ }Valid values @tab yes @tab yes @tab yes
+@item @w{ }@w{ }@w{ }@w{ }User- or system-missing values @tab --- @tab yes @tab yes
+@end multitable
+
+@node CTABLES Scale Missing Values
+@subsubsection Scale Missing Values
+
projects / pspp / blobdiff