| % File src/library/stats/man/ftable.formula.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2007 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{ftable.formula} |
| \alias{ftable.formula} |
| \title{Formula Notation for Flat Contingency Tables} |
| \description{Produce or manipulate a flat contingency table using |
| formula notation.} |
| \usage{ |
| \method{ftable}{formula}(formula, data = NULL, subset, na.action, \dots) |
| } |
| \arguments{ |
| \item{formula}{a formula object with both left and right hand sides |
| specifying the column and row variables of the flat table.} |
| \item{data}{a data frame, list or environment (or similar: see |
| \code{\link{model.frame}}) containing the variables |
| to be cross-tabulated, or a contingency table (see below).} |
| \item{subset}{an optional vector specifying a subset of observations |
| to be used. |
| Ignored if \code{data} is a contingency table.} |
| \item{na.action}{a function which indicates what should happen when |
| the data contain \code{NA}s. |
| Ignored if \code{data} is a contingency table.} |
| \item{\dots}{further arguments to the default ftable method may also |
| be passed as arguments, see \code{\link{ftable.default}}.} |
| } |
| \details{ |
| This is a method of the generic function \code{\link{ftable}}. |
| |
| The left and right hand side of \code{formula} specify the column and |
| row variables, respectively, of the flat contingency table to be |
| created. Only the \code{+} operator is allowed for combining the |
| variables. A \code{.} may be used once in the formula to indicate |
| inclusion of all the remaining variables. |
| |
| If \code{data} is an object of class \code{"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 \code{"ftable"}), it |
| should be a data frame or matrix, list or environment containing the |
| variables to be cross-tabulated. In this case, \code{na.action} is |
| applied to the data to handle missing values, and, after possibly |
| selecting a subset of the data as specified by the \code{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 \code{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. |
| } |
| \seealso{ |
| \code{\link{ftable}}, |
| \code{\link{ftable.default}}; |
| \code{\link{table}}. |
| } |
| \examples{ |
| Titanic |
| x <- ftable(Survived ~ ., data = Titanic) |
| x |
| ftable(Sex ~ Class + Age, data = x) |
| } |
| \keyword{category} |