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\name{xtabs}
\alias{xtabs}
\title{Cross tabulation}
\description{
\code{xtabs} creates a contingency table (optionally a sparse matrix) from
cross-classifying factors, usually contained in a data-frame-like object,
using a formula interface.
NOTE: This man page is for the \code{xtabs} \emph{S4 generic function}
defined in the \pkg{BiocGenerics} package.
See \code{?stats::\link[stats]{xtabs}} for the default method
(defined in the \pkg{stats} package).
Bioconductor packages can define specific methods for objects
not supported by the default method.
}
\usage{
xtabs(formula=~., data=parent.frame(), subset, sparse=FALSE,
na.action, exclude=c(NA, NaN), drop.unused.levels=FALSE)
}
\arguments{
\item{formula, subset, sparse, na.action, exclude, drop.unused.levels}{
See \code{?stats::\link[stats]{xtabs}} for a description of
these arguments.
}
\item{data}{
A data-frame-like object.
}
}
\value{
See \code{?stats::\link[stats]{xtabs}} for the value returned by the
default method.
Specific methods defined in Bioconductor packages should also
return the type of object returned by the default method.
}
\seealso{
\itemize{
\item \code{stats::\link[stats]{xtabs}} for the default \code{xtabs}
method.
\item \code{\link[methods]{showMethods}} for displaying a summary of the
methods defined for a given generic function.
\item \code{\link[methods]{selectMethod}} for getting the definition of
a specific method.
\item \link[IRanges]{xtabs,DataTable-method} in the \pkg{IRanges} package
for an example of a specific \code{xtabs} method (defined for
\link[IRanges]{DataTable} objects).
\item \link{BiocGenerics} for a summary of all the generics defined
in the \pkg{BiocGenerics} package.
}
}
\examples{
xtabs # note the dispatch on the 'data' arg only
showMethods("xtabs")
selectMethod("xtabs", "ANY") # the default method
}
\keyword{methods}
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