X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fstatistics.texi;h=602f0ad57444d76cc4a701c4c900e495e6a36a81;hb=4fd6d0378134d9653966258f44b0b0f8db15fbd5;hp=75de355bd07bd0d9a263b8d47f1ad3eb1dd847e8;hpb=cee6f0eb54144da7034566fa1bcdcee22337ae6a;p=pspp

diff --git a/doc/statistics.texi b/doc/statistics.texi
index 75de355bd0..602f0ad574 100644
--- a/doc/statistics.texi
+++ b/doc/statistics.texi
@@ -1014,12 +1014,6 @@ In @code{TABLE}, each of @var{rows}, @var{columns}, and @var{layers}
 is either empty or an axis expression that specifies one or more
 variables.  At least one must specify an axis expression.
 
-@menu
-* CTABLES Categorical Variable Basics::
-* CTABLES Scalar Variable Basics::
-* CTABLES Overriding Measurement Level::
-@end menu
-
 @node CTABLES Categorical Variable Basics
 @subsubsection Categorical Variables
 
@@ -1027,7 +1021,8 @@ An axis expression that names a categorical variable divides the data
 into cells according to the values of that variable.  When all the
 variables named on @code{TABLE} are categorical, by default each cell
 displays the number of cases that it contains, so specifying a single
-variable yields a frequency table:
+variable yields a frequency table, much like the output of the
+@code{FREQUENCIES} command (@pxref{FREQUENCIES}):
 
 @example
 CTABLES /TABLE=AgeGroup.
@@ -1036,7 +1031,8 @@ CTABLES /TABLE=AgeGroup.
 
 @noindent
 Specifying a row and a column categorical variable yields a
-crosstabulation:
+crosstabulation, much like the output of the @code{CROSSTABS} command
+(@pxref{CROSSTABS}):
 
 @example
 CTABLES /TABLE=AgeGroup BY qns3a.
@@ -1121,15 +1117,24 @@ decide whether to treat it as categorical or scalar.  Variables
 assigned the nominal or ordinal measurement level are treated as
 categorical, and scalar variables are treated as scalar.
 
-Use the @code{VARIABLE LEVEL} command to change a variable's
-measurement level (@pxref{VARIABLE LEVEL}).  To treat a variable as
-categorical or scalar only for one use on @code{CTABLES}, add
-@samp{[C]} or @samp{[S]}, respectively, after the variable name.  The
-following example shows how to analyze the scalar variable @code{qn20}
-as categorical:
+When @pspp{} reads data from a file in an external format, such as a
+text file, variables' measurement levels are often unknown.  If
+@code{CTABLES} runs when a variable has an unknown measurement level,
+it makes an initial pass through the data to guess measurement levels
+using the rules described earlier in this manual (@pxref{Measurement
+Level}).  Use the @code{VARIABLE LEVEL} command to set or change a
+variable's measurement level (@pxref{VARIABLE LEVEL}).
+
+To treat a variable as categorical or scalar only for one use on
+@code{CTABLES}, add @samp{[C]} or @samp{[S]}, respectively, after the
+variable name.  The following example shows the output when variable
+@code{qn20} is analyzed as scalar (the default for its measurement
+level) and as categorical:
 
 @example
-CTABLES /TABLE qn20 [C] BY qns3a.
+CTABLES
+    /TABLE qn20 BY qns3a
+    /TABLE qn20 [C] BY qns3a.
 @end example
 @psppoutput {ctables9}
 
@@ -1145,14 +1150,17 @@ sets.
 @subsection Data Summarization
 
 The @code{CTABLES} command allows the user to control how the data are
-summarized with summary specifications, which are enclosed in square
-brackets following a variable name on the @code{TABLE} subcommand.
-When all the variables are categorical, summary specifications can be
-given for the innermost nested variables on any one axis.  When a
-scalar variable is present, only the scalar variable may have summary
-specifications.  The following example includes a summary
-specification for column and row percentages for categorical
-variables, and mean and median for a scalar variable:
+summarized with @dfn{summary specifications}, syntax that lists one or
+more summary function names, optionally separated by commas, and which
+are enclosed in square brackets following a variable name on the
+@code{TABLE} subcommand.  When all the variables are categorical,
+summary specifications can be given for the innermost nested variables
+on any one axis.  When a scalar variable is present, only the scalar
+variable may have summary specifications.
+
+The following example includes a summary specification for column and
+row percentages for categorical variables, and mean and median for a
+scalar variable:
 
 @example
 CTABLES
@@ -1172,6 +1180,31 @@ CTABLES /TABLE=AgeGroup [COLPCT 'Gender %' PCT5.0,
 @end example
 @psppoutput {ctables11}
 
+In addition to the standard formats, @code{CTABLES} allows the user to
+specify the following special formats:
+
+@multitable {@code{NEGPAREN@i{w}.@i{d}}} {Encloses all numbers in parentheses.} {@t{(42.96%)}} {@t{(-42.96%)}}
+@item @code{NEGPAREN@i{w}.@i{d}}
+@tab Encloses negative numbers in parentheses.
+@tab @t{@w{    }42.96}
+@tab @t{@w{  }(42.96)}
+
+@item @code{NEQUAL@i{w}.@i{d}}
+@tab Adds a @code{N=} prefix.
+@tab @t{@w{  }N=42.96}
+@tab @t{@w{ }N=-42.96}
+
+@item @code{@code{PAREN@i{w}.@i{d}}}
+@tab Encloses all numbers in parentheses.
+@tab @t{@w{  }(42.96)}
+@tab @t{@w{ }(-42.96)}
+
+@item @code{PCTPAREN@i{w}.@i{d}}
+@tab Encloses all numbers in parentheses with a @samp{%} suffix.
+@tab @t{@w{ }(42.96%)}
+@tab @t{(-42.96%)}
+@end multitable
+
 Parentheses provide a shorthand to apply summary specifications to
 multiple variables.  For example, both of these commands:
 
@@ -1185,24 +1218,20 @@ produce the same output shown below:
 
 @psppoutput {ctables12}
 
-The following sections list the available summary functions.
-
-@menu
-* CTABLES Summary Functions for Individual Cells::
-* CTABLES Summary Functions for Groups of Cells::
-* CTABLES Summary Functions for Adjusted Weights::
-* CTABLES Unweighted Summary Functions::
-@end menu
+The following sections list the available summary functions.  After
+each function's name is given its default label and format.  If no
+format is listed, then the default format is the print format for the
+variable being summarized.
 
 @node CTABLES Summary Functions for Individual Cells
 @subsubsection Summary Functions for Individual Cells
 
-This section lists the summary functions that can be applied to
-individual cells in @code{CTABLES}.  Only one such summary function,
+This section lists the summary functions that consider only an
+individual cell in @code{CTABLES}.  Only one such summary function,
 @code{COUNT}, may be applied to both categorical and scale variables:
 
 @table @asis
-@item @code{COUNT} (``Count'')
+@item @code{COUNT} (``Count'', F40.0)
 The sum of weights in a cell.
 
 If @code{CATEGORIES} for one or more of the variables in a table
@@ -1252,7 +1281,7 @@ The standard deviation.
 @item @code{SUM} (``Sum'')
 The sum.
 
-@item @code{TOTALN} (``Total N'')
+@item @code{TOTALN} (``Total N'', F40.0)
 The sum of weights in a cell.
 
 For scale data, @code{COUNT} and @code{TOTALN} are the same.
@@ -1264,7 +1293,7 @@ Options}), or user-missing values excluded because
 @code{MISSING=EXCLUDE} is in effect on @code{CATEGORIES}, or
 system-missing values.  @code{COUNT} does not count these.
 
-@item @code{VALIDN} (``Valid N'')
+@item @code{VALIDN} (``Valid N'', F40.0)
 The sum of valid count weights in included categories.
 
 @code{VALIDN} does not count missing values regardless of whether they
@@ -1325,13 +1354,13 @@ 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} %'')
+@item @code{@i{area}PCT} or @code{@i{area}PCT.COUNT} (``@i{Area} %'', PCT40.1)
 A percentage of total counts within @var{area}.
 
-@item @code{@i{area}PCT.VALIDN} (``@i{Area} Valid N %'')
+@item @code{@i{area}PCT.VALIDN} (``@i{Area} Valid N %'', PCT40.1)
 A percentage of total counts for valid values within @var{area}.
 
-@item @code{@i{area}PCT.TOTALN} (``@i{Area} Total N %'')
+@item @code{@i{area}PCT.TOTALN} (``@i{Area} Total N %'', PCT40.1)
 A percentage of total counts for all values within @var{area}.
 @end table
 
@@ -1339,7 +1368,7 @@ 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 %'')
+@item @code{@i{area}PCT.SUM} (``@i{Area} Sum %'', PCT40.1)
 Percentage of the sum of the values within @var{area}.
 @end table
 
@@ -1353,13 +1382,13 @@ the summary function without the @samp{E}-prefix:
 
 @itemize @bullet
 @item
-@code{ECOUNT} (``Adjusted Count'')
+@code{ECOUNT} (``Adjusted Count'', F40.0)
 
 @item
-@code{ETOTALN} (``Adjusted Total N'')
+@code{ETOTALN} (``Adjusted Total N'', F40.0)
 
 @item
-@code{EVALIDN} (``Adjusted Valid N'')
+@code{EVALIDN} (``Adjusted Valid N'', F40.0)
 @end itemize
 
 @node CTABLES Unweighted Summary Functions
@@ -1371,16 +1400,16 @@ counts:
 
 @itemize @bullet
 @item
-@code{UCOUNT} (``Unweighted Count'')
+@code{UCOUNT} (``Unweighted Count'', F40.0)
 
 @item
-@code{U@i{area}PCT} or @code{U@i{area}PCT.COUNT} (``Unweighted @i{Area} %'')
+@code{U@i{area}PCT} or @code{U@i{area}PCT.COUNT} (``Unweighted @i{Area} %'', PCT40.1)
 
 @item
-@code{U@i{area}PCT.VALIDN} (``Unweighted @i{Area} Valid N %'')
+@code{U@i{area}PCT.VALIDN} (``Unweighted @i{Area} Valid N %'', PCT40.1)
 
 @item
-@code{U@i{area}PCT.TOTALN} (``Unweighted @i{Area} Total N %'')
+@code{U@i{area}PCT.TOTALN} (``Unweighted @i{Area} Total N %'', PCT40.1)
 
 @item
 @code{UMEAN} (``Unweighted Mean'')
@@ -1395,7 +1424,7 @@ counts:
 @code{UMODE} (``Unweight Mode'')
 
 @item
-@code{U@i{area}PCT.SUM} (``Unweighted @i{Area} Sum %'')
+@code{U@i{area}PCT.SUM} (``Unweighted @i{Area} Sum %'', PCT40.1)
 
 @item
 @code{UPTILE} @i{n} (``Unweighted Percentile @i{n}'') 
@@ -1410,15 +1439,63 @@ counts:
 @code{USUM} (``Unweighted Sum'')
 
 @item
-@code{UTOTALN} (``Unweighted Total N'')
+@code{UTOTALN} (``Unweighted Total N'', F40.0)
 
 @item
-@code{UVALIDN} (``Unweighted Valid N'')
+@code{UVALIDN} (``Unweighted Valid N'', F40.0)
 
 @item
-@code{UVARIANCE} (``Unweighted Variance'')
+@code{UVARIANCE} (``Unweighted Variance'', F40.0)
 @end itemize
 
+@node CTABLES Summarizing Missing Values
+@subsubsection Summarizing Missing Values
+
+CTABLES treats missing values in categorical and scale variables
+differently.  For categorical variables, in most cases values that are
+valid and in included categories are analyzed, and values that are
+missing or in excluded categories are not analyzed.  (@xref{CTABLES
+Per-Variable Category Options}), for information on included and
+excluded categories.)  The following chart, in which cells that
+contain ``yes'' indicate that a value is analyzed, and the notes below
+it give the exact rules:
+
+@multitable {@headitemfont{System-Missing}} {Included Category} {Excluded Category}
+@headitem                           @tab Included Category    @tab Excluded Category
+@item @headitemfont{Valid}          @tab yes                  @tab ---
+@item @headitemfont{User-Missing}   @tab yes [*]              @tab --- [+]
+@item @headitemfont{System-Missing} @tab n/a [#]              @tab --- [+]
+@end multitable
+
+@table @asis
+@item [*]
+Exceptions: The ``@t{VALIDN}'' summary functions (@code{VALIDN},
+@code{EVALIDN}, @code{UVALIDN}, @code{@i{area}PCT.VALIDN}, and
+@code{U@i{area}PCT.VALIDN}), which only count valid values in included
+categories.
+
+@item [+]
+Exceptions: The ``@t{TOTALN}'' summary functions (@code{TOTALN},
+@code{ETOTALN}, @code{UTOTALN}, @code{@i{area}PCT.TOTALN}), and
+@code{U@i{area}PCT.TOTALN}, which count all values (valid and missing)
+in included categories and missing (but not valid) values in excluded
+categories.
+
+@item [#]
+System-missing values are never in included categories.
+@end table
+
+@noindent
+The following table provides another view of the same information:
+
+@multitable {Missing values in excluded categories} {@code{VALIDN}} {other} {@code{TOTALN}}
+@headitem @tab @code{VALIDN} @tab other @tab @code{TOTALN}
+@item Valid values in included categories   @tab yes @tab yes @tab yes
+@item Missing values in included categories @tab --- @tab yes @tab yes
+@item Missing values in excluded categories @tab --- @tab --- @tab yes
+@item Valid values in excluded categories   @tab --- @tab --- @tab ---
+@end multitable
+
 @node CTABLES Statistics Positions and Labels
 @subsection Statistics Positions and Labels
 
@@ -1485,8 +1562,8 @@ CTABLES /TABLE AgeGroup BY qns3a.
 
 @t{ROWLABELS=OPPOSITE} or @t{COLLABELS=OPPOSITE} move row or column
 variable category labels, respectively, to the opposite axis.  The
-setting affects only the innermost variable on the given axis.  For
-example:
+setting affects only the innermost variable or variables, which must
+be categorical, on the given axis.  For example:
 
 @example
 CTABLES /TABLE AgeGroup BY qns3a /CLABELS ROWLABELS=OPPOSITE.
@@ -1500,6 +1577,50 @@ column variable category labels, respectively, to the layer axis.
 Only one axis's labels may be moved, whether to the opposite axis or
 to the layer axis.
 
+@subsubheading Effect on Summary Statistics
+
+@code{CLABELS} primarily affects the appearance of tables, not the
+data displayed in them.  However, @code{CTABLES} can affect the values
+displayed for statistics that summarize areas of a table, since it can
+change the definitions of these areas.
+
+For example, consider the following syntax and output:
+
+@example
+CTABLES /TABLE AgeGroup BY qns3a [ROWPCT, COLPCT].
+@end example
+@psppoutput {ctables23}
+
+@noindent
+Using @code{COLLABELS=OPPOSITE} changes the definitions of rows and
+columns, so that column percentages display what were previously row
+percentages and the new row percentages become meaningless (because
+there is only one cell per row):
+
+@example
+CTABLES
+    /TABLE AgeGroup BY qns3a [ROWPCT, COLPCT]
+    /CLABELS COLLABELS=OPPOSITE.
+@end example
+@psppoutput {ctables24}
+
+@subsubheading Moving Categories for Stacked Variables
+
+If @code{CLABELS} moves category labels from an axis with stacked
+variables, the variables that are moved must have the same category
+specifications (@pxref{CTABLES Per-Variable Category Options}) and the
+same value labels.
+
+The following shows both moving stacked category variables and
+adapting to the changing definitions of rows and columns:
+
+@example
+CTABLES /TABLE (qn105ba + qn105bb) [COLPCT].
+CTABLES /TABLE (qn105ba + qn105bb) [ROWPCT]
+  /CLABELS ROW=OPPOSITE.
+@end example
+@psppoutput {ctables25}
+
 @node CTABLES Per-Variable Category Options
 @subsection Per-Variable Category Options
 
@@ -1523,7 +1644,7 @@ variables.  @code{CATEGORIES} applies to the table produced by the
 
 @code{CATEGORIES} does not apply to scalar variables.
 
-@t{VARIABLES} is required.  List the variables for the subcommand
+@t{VARIABLES} is required and must list the variables for the subcommand
 to affect.
 
 There are two way to specify the Categories to include and their sort
@@ -1570,7 +1691,7 @@ A computed category name (@pxref{CTABLES Computed Categories}).
 
 Additional forms, described later, allow for subtotals.
 If multiple elements of the list cover a given category, the last one
-in the list is considered to be a match.
+in the list takes precedence.
 
 @item Implicit categories.
 Without an explicit list of categories, @pspp{} sorts
@@ -1579,13 +1700,15 @@ categories automatically.
 The @code{KEY} setting specifies the sort key.  By default, or with
 @code{KEY=VALUE}, categories are sorted by default.  Categories may
 also be sorted by value label, with @code{KEY=LABEL}, or by the value
-of a summary function, e.g.@: @code{KEY=COUNT}.  For summary
-functions, a variable name may be specified in parentheses, e.g.@:
-@code{KEY=MAXIUM(qnd1)}, and this is required for functions that apply
-only to scalar variables.  The @code{PTILE} function also requires a
-percentage argument, e.g.@: @code{KEY=PTILE(qnd1, 90)}.  Only summary
-functions used in the table may be used, except that @code{COUNT} is
-always allowed.
+of a summary function, e.g.@: @code{KEY=COUNT}.
+@ignore  @c Not yet implemented
+For summary functions, a variable name may be specified in
+parentheses, e.g.@: @code{KEY=MAXIUM(qnd1)}, and this is required for
+functions that apply only to scalar variables.  The @code{PTILE}
+function also requires a percentage argument, e.g.@:
+@code{KEY=PTILE(qnd1, 90)}.  Only summary functions used in the table
+may be used, except that @code{COUNT} is always allowed.
+@end ignore
 
 By default, or with @code{ORDER=A}, categories are sorted in ascending
 order.  Specify @code{ORDER=D} to sort in descending order.
@@ -1598,9 +1721,10 @@ user-missing values.  The system-missing value is always excluded.
 @subsubheading Totals and Subtotals
 
 @code{CATEGORIES} also controls display of totals and subtotals.
-Totals are not displayed by default, or with @code{TOTAL=NO}.  Specify
-@code{TOTAL=YES} to display a total.  By default, the total is labeled
-``Total''; use @code{LABEL="@i{label}"} to override it.
+Totals are not displayed with @code{TOTAL=NO}, which is also the
+default.  Specify @code{TOTAL=YES} to display a total.  By default,
+the total is labeled ``Total''; use @code{LABEL="@i{label}"} to
+override it.
 
 Subtotals are also not displayed by default.  To add one or more
 subtotals, use an explicit category list and insert @code{SUBTOTAL} or
@@ -1611,16 +1735,18 @@ categories that make up the subtotal.  Either way, the default label
 is ``Subtotal'', use @code{SUBTOTAL="@i{label}"} or
 @code{HSUBTOTAL="@i{label}"} to specify a custom label.
 
-By default, or with @code{POSITION=AFTER}, totals come after the last
-category and subtotals apply to categories that precede them.  With
-@code{POSITION=BEFORE}, totals come before the first category and
-subtotals apply to categories that follow them.
+By default, or with @code{POSITION=AFTER}, totals are displayed in the
+output after the last category and subtotals apply to categories that
+precede them.  With @code{POSITION=BEFORE}, totals come before the
+first category and subtotals apply to categories that follow them.
 
 Only categorical variables may have totals and subtotals.  Scalar
 variables may be ``totaled'' indirectly by enabling totals and
 subtotals on a categorical variable within which the scalar variable is
 summarized.
 
+@c TODO Specifying summaries for totals and subtotals
+
 @subsubheading Categories Without Values
 
 Some categories might not be included in the data set being analyzed.
@@ -1630,9 +1756,10 @@ younger'' age group.  By default, or with @code{EMPTY=INCLUDE},
 them, specify @code{EMPTY=EXCLUDE}.
 
 For implicit categories, empty categories potentially include all the
-values with labels for a given variable; for explicit categories, they
-include all the values listed individually and all labeled values
-covered by ranges or @code{MISSING} or @code{OTHERNM}.
+values with value labels for a given variable; for explicit
+categories, they include all the values listed individually and all
+values with value labels that are covered by ranges or @code{MISSING}
+or @code{OTHERNM}.
 
 @node CTABLES Titles
 @subsection Titles
@@ -1645,10 +1772,33 @@ covered by ranges or @code{MISSING} or @code{OTHERNM}.
 @end display
 
 The @code{TITLES} subcommand sets the title, caption, and corner text
-for the table output for the previous @code{TABLE} subcommand.  The
-title appears above the table, the caption below the table, and the
-corner text appears in the table's upper left corner.  By default, the
-title is ``Custom Tables'' and the caption and corner text are empty.
+for the table output for the previous @code{TABLE} subcommand.  Any
+number of strings may be specified for each kind of text, with each
+string appearing on a separate line in the output.  The title appears
+above the table, the caption below the table, and the corner text
+appears in the table's upper left corner.  By default, the title is
+``Custom Tables'' and the caption and corner text are empty.  With
+some table output styles, the corner text is not displayed.
+
+The strings provided in this subcommand may contain the following
+macro-like keywords that @pspp{} substitutes at the time that it runs
+the command:
+
+@table @code @c (
+@item )DATE
+The current date, e.g.@: MM/DD/YY.  The format is locale-dependent.
+
+@c (
+@item )TIME
+The current time, e.g.@: HH:MM:SS.  The format is locale-dependent.
+
+@c (
+@item )TABLE
+The expression specified on the @code{TABLE} command.  Summary
+and measurement level specifications are omitted, and variable labels are used in place of variable names.
+@end table
+
+@c TODO example
 
 @node CTABLES Table Formatting
 @subsection Table Formatting
@@ -1667,13 +1817,13 @@ The @code{FORMAT} subcommand, which must precede the first
 tables.  @code{FORMAT} and all of its settings are optional.
 
 Use @code{MINCOLWIDTH} and @code{MAXCOLWIDTH} to control the minimum
-or maximum width of columns in output tables.  By default, or with
+or maximum width of columns in output tables.  By default, with
 @code{DEFAULT}, column width varies based on content.  Otherwise,
 specify a number for either or both of these settings.  If both are
-specified, @code{MAXCOLWIDTH} must be bigger than @code{MINCOLWIDTH}.
-The default unit, or with @code{UNITS=POINTS}, is points (1/72 inch),
-but specify @code{UNITS=INCHES} to use inches or @code{UNITS=CM} for
-centimeters.
+specified, @code{MAXCOLWIDTH} must be greater than or equal to
+@code{MINCOLWIDTH}.  The default unit, or with @code{UNITS=POINTS}, is
+points (1/72 inch), or specify @code{UNITS=INCHES} to use inches or
+@code{UNITS=CM} for centimeters.
 
 By default, or with @code{EMPTY=ZERO}, zero values are displayed in
 their usual format.  Use @code{EMPTY=BLANK} to use an empty cell
@@ -1703,7 +1853,7 @@ variables listed on @code{VARIABLES}.  The supported values are:
 
 @table @code
 @item DEFAULT
-Uses the setting from @ref{SET TVARS}.
+Use the setting from @code{SET TVARS} (@pxref{SET TVARS}).
 
 @item NAME
 Show only a variable name.
@@ -1802,30 +1952,33 @@ in @code{EXPR(@dots{})}.  A postcompute expression consists of:
 This form evaluates to the summary statistic for @i{category}, e.g.@:
 @code{[1]} evaluates to the value of the summary statistic associated
 with category 1.  The @i{category} may be a number, a quoted string,
-or a quoted time or date value, and all of the categories for a given
-postcompute must have the same form.
+or a quoted time or date value.  All of the categories for a given
+postcompute must have the same form.  The category must appear in all
+the @code{CATEGORIES} list in which the postcompute is used.
 
 @item [@i{min} THRU @i{max}]
 @itemx [LO THRU @i{max}]
 @itemx [@i{min} THRU HI]
 @itemx MISSING
 @itemx OTHERNM
-These forms evaluate to the summary statistics for categories matching
-the given syntax, as described in previous sections (@pxref{CTABLES
-Explicit Category List}).  If more than one category matches, their
-values are summed.
+These forms evaluate to the summary statistics for a category
+specified with the same syntax, as described in previous section
+(@pxref{CTABLES Explicit Category List}).  The category must appear in
+all the @code{CATEGORIES} list in which the postcompute is used.
 
 @item SUBTOTAL
 The summary statistic for the subtotal category.  This form is allowed
-only for variables with exactly one subtotal.
+only if the @code{CATEGORIES} lists that include this postcompute have
+exactly one subtotal.
 
 @item SUBTOTAL[@i{index}]
 The summary statistic for subtotal category @i{index}, where 1 is the
 first subtotal, 2 is the second, and so on.  This form may be used for
-any number of subtotals.
+@code{CATEGORIES} lists with any number of subtotals.
 
 @item TOTAL
-The summary statistic for the total.
+The summary statistic for the total.  The @code{CATEGORIES} lsits that
+include this postcompute must have a total enabled.
 
 @item @i{a} + @i{b}
 @itemx @i{a} - @i{b}
@@ -1892,14 +2045,16 @@ by computed categories are displayed like other categories.  Use
 The @code{WEIGHT} subcommand is optional and must appear before
 @code{TABLE}.  If it appears, it must name a numeric variable, known
 as the @dfn{effective base weight} or @dfn{adjustment weight}.  The
-effective base weight variable is used for the @code{ECOUNT},
-@code{ETOTALN}, and @code{EVALIDN} summary functions.
-
-Cases with zero, missing, or negative effective base weight are
-excluded from all analysis.
+effective base weight variable stands in for the dictionary's weight
+variable (@pxref{WEIGHT}), if any, in most calculations in
+@code{CTABLES}.  The only exceptions are the @code{COUNT},
+@code{TOTALN}, and @code{VALIDN} summary functions, which use the
+dictionary weight instead.
 
 Weights obtained from the @pspp{} dictionary are rounded to the
-nearest integer.  Effective base weights are not rounded.
+nearest integer at the case level.  Effective base weights are not
+rounded.  Regardless of the weighting source, @pspp{} does not analyze
+cases with zero, missing, or negative effective weights.
 
 @node CTABLES Hiding Small Counts
 @subsection Hiding Small Counts