| ftable {base} | R Documentation |
Create and manipulate ``flat'' contingency tables.
ftable(..., exclude = c(NA, NaN), row.vars = NULL, col.vars = NULL) ftable2table(x)
... |
R objects which can be interpreted as factors (including
character strings), or a list (or data frame) whose components can
be so interpreted, or a contingency table object of class
"table" or "ftable". |
exclude |
values to use in the exclude argument of factor
when interpreting non-factor objects. |
row.vars |
a vector of integers giving the numbers of the variables, or a character vector giving the names of the variables to be used for the rows of the flat contingency table. |
col.vars |
a vector of integers giving the numbers of the variables, or a character vector giving the names of the variables to be used for the columns of the flat contingency table. |
x |
an arbitrary R object. |
ftable creates ``flat'' contingency tables. Similar to the
usual contingency tables, these contain the counts of each combination
of the levels of the variables (factors) involved. This information
is then re-arranged as a matrix whose rows and columns correspond to
unique combinations of the levels of the row and column variables (as
specified by row.vars and col.vars, respectively). The
combinations are created by looping over the variables in reverse
order (so that the levels of the ``left-most'' variable vary the
slowest). Displaying a contingency table in this flat matrix form
(via print.ftable, the print method for objects of class
"ftable") is often preferable to showing it as a
higher-dimensional array.
ftable is a generic function. Its default method,
ftable.default, first creates a contingency table in array
form from all arguments except row.vars and col.vars.
If the first argument is of class "table", it represents a
contingency table and is used as is; if it is a flat table of class
"ftable", the information it contains is converted to the usual
array representation using ftable2table. Otherwise, the
arguments should be R objects which can be interpreted as factors
(including character strings), or a list (or data frame) whose
components can be so interpreted, which are cross-tabulated using
table. Then, the arguments row.vars and
col.vars are used to collapse the contingency table into flat
form. If neither of these two is given, the last variable is used for
the columns. If both are given and their union is a proper subset of
all variables involved, the other variables are summed out.
Function ftable.formula provides a formula method for
creating flat contingency tables.
ftable2table converts a contingency table in flat matrix form
to one in standard array form.
ftable returns an object of class "ftable", which is a
matrix with counts of each combination of the levels of variables with
information on the names and levels of the (row and columns) variables
stored as attributes "row.vars" and "col.vars".
ftable.formula for the formula interface (which allows a
data = . argument);
table for ``ordinary'' cross-tabulation.
## Start with a contingency table.
data(Titanic)
ftable(Titanic, row.vars = 1:3)
ftable(Titanic, row.vars = 1:2, col.vars = "Survived")
ftable(Titanic, row.vars = 2:1, col.vars = "Survived")
## Start with a data frame.
data(mtcars)
x <- ftable(mtcars[c("cyl", "vs", "am", "gear")])
x
ftable(x, row.vars = c(2, 4))