ftable.formula
Formula Notation for Flat Contingency Tables
Produce or manipulate a flat contingency table using formula notation.
 Keywords
 category
Usage
"ftable"(formula, data = NULL, subset, na.action, ...)
Arguments
 formula
 a formula object with both left and right hand sides specifying the column and row variables of the flat table.
 data
 a data frame, list or environment (or similar: see
model.frame
) containing the variables to be crosstabulated, or a contingency table (see below).  subset
 an optional vector specifying a subset of observations
to be used.
Ignored if
data
is a contingency table.  na.action
 a function which indicates what should happen when
the data contain
NA
s. Ignored ifdata
is a contingency table.  ...
 further arguments to the default ftable method may also
be passed as arguments, see
ftable.default
.
Details
This is a method of the generic function ftable
.
The left and right hand side of formula
specify the column and
row variables, respectively, of the flat contingency table to be
created. Only the +
operator is allowed for combining the
variables. A .
may be used once in the formula to indicate
inclusion of all the remaining variables.
If data
is an object of class "table"
or an array with
more than 2 dimensions, it is taken as a contingency table, and hence
all entries should be nonnegative. Otherwise, if it is not a flat
contingency table (i.e., an object of class "ftable"
), it
should be a data frame or matrix, list or environment containing the
variables to be crosstabulated. In this case, na.action
is
applied to the data to handle missing values, and, after possibly
selecting a subset of the data as specified by the subset
argument, a contingency table is computed from the variables.
The contingency table is then collapsed to a flat table, according to
the row and column variables specified by formula
.
Value

A flat contingency table which contains the counts of each combination
of the levels of the variables, collapsed into a matrix for suitably
displaying the counts.
See Also
Examples
library(stats)
Titanic
x < ftable(Survived ~ ., data = Titanic)
x
ftable(Sex ~ Class + Age, data = x)