ftable.formula             package: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
          'model.frame') containing the variables to be
          cross-tabulated, 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 if 'data' 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 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)

