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\name{Extract.sparse3Darray}
\alias{[.sparse3Darray}
\alias{[<-.sparse3Darray}
\title{Extract or Replace Entries in a Sparse Array}
\description{
Extract or replace entries in a sparse three-dimensional array.
}
\usage{
\method{[}{sparse3Darray}(x, i, j, k, drop=TRUE, \dots)
\method{[}{sparse3Darray}(x, i, j, k, \dots) <- value
}
\arguments{
\item{x}{
Sparse three-dimensional array
(object of class \code{"sparse3Darray"}).
}
\item{i,j,k}{
Subset indices for each dimension of the array. See Details.
}
\item{value}{
Replacement value for the subset.
}
\item{drop}{
Logical value indicating whether to return a lower-dimensional
object (matrix or vector) when appropriate.
}
\item{\dots}{
Ignored. This argument is required for compatibility
with the generic function.
}
}
\value{
\code{[.sparse3Darray} returns either
a sparse three-dimensional array (class \code{"sparse3Darray"}),
a sparse matrix (class \code{sparseMatrix} in the \pkg{Matrix} package),
a sparse vector (class \code{sparseVector} in the \pkg{Matrix} package),
or in some cases a full array, matrix or vector.
\code{[<-.sparse3Darray} returns another sparse three-dimensional
array.
}
\details{
These functions are defined for a sparse three-dimensional array \code{x}.
They extract a designated subset of the array,
or replace the values in the designated subset.
The function \code{[.sparse3Darray} is a method for the generic
subset extraction operator \code{\link{[}}.
The function \code{[<-.sparse3Darray} is a method for the generic
subset replacement operator \code{\link{[<-}}.
These methods use the same indexing rules
as the subset operator for full arrays:
\itemize{
\item If \code{i}, \code{j} and \code{k} are integer vectors,
the subset is the Cartesian product (i.e. all cells in the array
identified by an entry of \code{i}, an entry of \code{j} and
an entry of \code{k}).
\item Some or all of the arguments \code{i}, \code{j} and \code{k}
may be missing from the call; a missing index argument is
interpreted as meaning that all possible values of that index are
allowed.
\item Arguments \code{i}, \code{j} and \code{k} may be logical
vectors (with the value \code{TRUE} assigned to entries that should
be included).
\item Arguments \code{i}, \code{j} and \code{k} may be
character vectors with entries matching the corresponding
\code{dimnames}.
\item Argument \code{i} may be an integer matrix with 3 columns
(and the arguments \code{j,k} should be absent).
Each row of the matrix contains the indices
of one cell in the array.
}
If the designated subset lies within the array bounds, then
the result of \code{[} will be a sparse three-dimensional array,
sparse matrix or sparse vector. If \code{drop=FALSE} the result
will always be three-dimensional; if \code{drop=TRUE} (the default)
the result will be reduced to two or one dimensions when appropriate.
If the designated subset \emph{does not} lie within the array bounds, then
the result of \code{[} will be a full three-dimensional array,
matrix or vector containing \code{NA} values at the positions that
were outside the array bounds.
The result of \code{[<-} is always a sparse three-dimensional array.
If the designated subset did not lie within the array bounds of
\code{x}, then the array bounds will be extended (with a warning message).
}
\seealso{
\code{\link{sparse3Darray}},
\code{\link{methods.sparse3Darray}}.
}
\examples{
M <- sparse3Darray(i=1:4, j=sample(1:4, replace=TRUE),
k=c(1,2,1,2), x=1:4, dims=c(5,5,2))
dimnames(M) <- list(letters[1:5], LETTERS[1:5], c("yes", "no"))
M[ 3:4, , ]
M[ 3:4, 2:4, ]
M[ 4:3, 4:2, 1:2]
M[, 3, ]
}
\author{
\spatstatAuthors.
}
\keyword{array}
\keyword{manip}
\concept{sparse}
|
