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\name{array}
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\alias{array}
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\alias{as.array}
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\alias{is.array}
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\title{Multi-way Arrays}
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\description{
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  Creates or tests for arrays.
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}
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\usage{
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array(data = NA, dim = length(data), dimnames = NULL)
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as.array(x)
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is.array(x)
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}
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\arguments{
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  \item{data}{a vector (including a list) giving data to fill the array.}
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  \item{dim}{the dim attribute for the array to be created, that is a
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    vector of length one or more giving the maximal indices in
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    each dimension.}
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  \item{dimnames}{the names for the dimensions. This is a list with one
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    component for each dimension, either NULL or a character vector of
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    the length given by \code{dim} for that dimension.  The list can be
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    names, and the names will be used as names for the dimensions.}
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  \item{x}{an \R object.}
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}
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\value{
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  \code{array} returns an array with the extents specified in \code{dim}
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  and naming information in \code{dimnames}.  The values in \code{data} are
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  taken to be those in the array with the leftmost subscript moving
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  fastest.  If there are too few elements in \code{data} to fill the array,
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  then the elements in \code{data} are recycled.  If \code{data} has
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  length zero, \code{NA} of an appropriate type is used for atomic
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  vectors and \code{NULL} for lists.
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  \code{as.array()} coerces its argument to be an array by attaching a
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  \code{\link{dim}} attribute to it.  It also attaches
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  \code{\link{dimnames}} if \code{x} has \code{\link{names}}.
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  The sole purpose of this is to make it possible to access the
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  \code{dim}[names] attribute at a later time.
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  \code{is.array} returns \code{TRUE} or \code{FALSE} depending on
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  whether its argument is an array (i.e., has a \code{dim} attribute)
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  or not. It is generic: you can write methods to handle
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  specific classes of objects, see \link{InternalMethods}.
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}
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\references{
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  Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
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  \emph{The New S Language}.
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  Wadsworth \& Brooks/Cole.
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}
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\seealso{
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  \code{\link{aperm}}, \code{\link{matrix}},
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  \code{\link{dim}}, \code{\link{dimnames}}.
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}
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\examples{
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dim(as.array(letters))
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array(1:3, c(2,4)) # recycle 1:3 "2 2/3 times"
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#     [,1] [,2] [,3] [,4]
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#[1,]    1    3    2    1
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#[2,]    2    1    3    2
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}
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\keyword{array}