+@node CTABLES Summary Functions for Groups of Cells
+@subsubsection Summary Functions for Groups of Cells
+
+These summary functions summarize over multiple cells within an area
+of the output chosen by the user and specified as part of the function
+name. The following basic @var{area}s are supported, in decreasing
+order of size:
+
+@table @code
+@item TABLE
+A @dfn{section}. Stacked variables divide sections of the output from
+each other. sections may span multiple layers.
+
+@item LAYER
+A section within a single layer.
+
+@item SUBTABLE
+A @dfn{subtable}, whose contents are the cells that pair an innermost
+row variable and an innermost column variable within a single layer.
+@end table
+
+The following shows how the output for the table expression @code{qn61
+> qn57 BY qnd7a > qn86 + qn64b BY qns3a}@footnote{This is not
+necessarily a meaningful table, so for clarity variable labels are
+omitted.} is divided up into @code{TABLE}, @code{LAYER}, and
+@code{SUBTABLE} areas. Each unique value for Table ID is one section,
+and similarly for Layer ID and Subtable ID. Thus, this output has two
+@code{TABLE} areas (one for @code{qnd7a} and one for @code{qn64b}),
+four @code{LAYER} areas (for those two variables, per layer), and 12
+@code{SUBTABLE} areas.
+@psppoutput {ctables22}
+
+@code{CTABLES} also supports the following @var{area}s that further
+divide a subtable or a layer within a section:
+
+@table @code
+@item LAYERROW
+@itemx LAYERCOL
+A row or column, respectively, in one layer of a section.
+
+@item ROW
+@itemx COL
+A row or column, respectively, in a subtable.
+@end table
+
+The following summary functions for groups of cells are available for
+each @var{area} described above, for both categorical and scale
+variables:
+
+@table @asis
+@item @code{@i{area}PCT} or @code{@i{area}PCT.COUNT} (``@i{Area} %'')
+A percentage of total counts within @var{area}.
+
+@item @code{@i{area}PCT.VALIDN} (``@i{Area} Valid N %'')
+A percentage of total counts for valid values within @var{area}.
+
+@item @code{@i{area}PCT.TOTALN} (``@i{Area} Total N %'')
+A percentage of total counts for all values within @var{area}.
+@end table
+
+Scale variables and totals and subtotals for categorical variables may
+use the following additional group cell summary function:
+
+@table @asis
+@item @code{@i{area}PCT.SUM} (``@i{Area} Sum %'')
+Percentage of the sum of the values within @var{area}.
+@end table
+
+@node CTABLES Summary Functions for Adjusted Weights
+@subsubsection Summary Functions for Adjusted Weights
+