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slice.index(x, MARGIN)
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slice.index(x, MARGIN)
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}
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}
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\arguments{
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\arguments{
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  \item{x}{an array.  If \code{x} has no dimension attribute, it is
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  \item{x}{an array.  If \code{x} has no dimension attribute, it is
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    considered a one-dimensional array.}
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    considered a one-dimensional array.}
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  \item{MARGIN}{an integer giving the dimension number to slice by.}
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  \item{MARGIN}{an integer vector giving the dimension numbers to slice
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    by.}
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}
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}
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\value{
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\value{
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  An integer array \code{y} with dimensions corresponding to those of
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  An integer array \code{y} with dimensions corresponding to those of
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  \code{x}.
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}
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\details{
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  If \code{MARGIN} gives a single dimension, then all elements of slice
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  \code{x} such that all elements of slice number \code{i} with respect
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  number \code{i} with respect to this have value \code{i}.  In general,
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  slice numbers are obtained by numbering all combinations of indices in
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  the dimensions given by \code{MARGIN} in column-major order.  I.e.,
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  with \eqn{m_1}, \ldots, \eqn{m_k} the dimension numbers (elements of
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  \code{MARGIN}) sliced by and \eqn{d_{m_1}}, \ldots, \eqn{d_{m_k}} the
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  corresponding extents, and \eqn{n_1 = 1}, \eqn{n_2 = d_{m_1}}, \ldots,
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  \eqn{n_k = d_{m_1} \cdots d_{m_{k-1}}}{n_k = d_{m_1} \dots d_{m_{k-1}}},
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  the number of the slice where dimension \eqn{m_1} has value \eqn{i_1},
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  to dimension \code{MARGIN} have value \code{i}.
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  \ldots, dimension \eqn{m_k} has value \eqn{i_k} is
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  \eqn{1 + n_1 (i_1 - 1) + \cdots + n_k (i_k - 1)}{1 + n_1 (i_1 - 1) +
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    \dots + n_k (i_k - 1)}.
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}
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}
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\seealso{
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\seealso{
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  \code{\link{row}} and \code{\link{col}} for determining row and column
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  \code{\link{row}} and \code{\link{col}} for determining row and column
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  indexes; in fact, these are special cases of \code{slice.index}
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  indexes; in fact, these are special cases of \code{slice.index}
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  corresponding to \code{MARGIN} equal to 1 and 2, respectively when \code{x}
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  corresponding to \code{MARGIN} equal to 1 and 2, respectively when
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  is a matrix.
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  \code{x} is a matrix.
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}
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}
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\examples{
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\examples{
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x <- array(1 : 24, c(2, 3, 4))
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x <- array(1 : 24, c(2, 3, 4))
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slice.index(x, 2)
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slice.index(x, 2)
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slice.index(x, c(1, 3))
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## When slicing by dimensions 1 and 3, slice index 5 is obtained for
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## dimension 1 has value 1 and dimension 3 has value 3 (see above):
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which(slice.index(x, c(1, 3)) == 5, arr.ind = TRUE)
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}
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}
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\keyword{array}
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\keyword{array}