| ftable.formula {stats} | R Documentation |
Formula Notation for Flat Contingency Tables
Description
Produce or manipulate a flat contingency table using formula notation.
Usage
## S3 method for class 'formula'
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
|
subset |
an optional vector specifying a subset of observations
to be used.
Ignored if |
na.action |
a function which indicates what should happen when
the data contain |
... |
further arguments to the 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 cross-tabulated. 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
ftable,
ftable.default;
table.
Examples
Titanic
x <- ftable(Survived ~ ., data = Titanic)
x
ftable(Sex ~ Class + Age, data = x)