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\name{read_block}
\alias{read_block}
\alias{read_block,ANY-method}
\alias{write_block}
\alias{write_block,ANY-method}
\alias{is_sparse}
\alias{read_sparse_block}
\alias{read_sparse_block,ANY-method}
\alias{read_sparse_block,SparseArraySeed-method}
\alias{write_sparse_block}
\alias{write_sparse_block,ANY-method}
\title{Read/write blocks of array data}
\description{
2 utilities for reading/writing blocks from/to an array-like object.
}
\usage{
read_block(x, viewport)
write_block(x, viewport, block)
}
\arguments{
\item{x}{
An array-like object.
}
\item{viewport}{
An \link{ArrayViewport} object.
}
\item{block}{
An ordinary array of the same dimensions as \code{viewport}.
}
}
\seealso{
\itemize{
\item \link{ArrayViewport} objects.
\item \code{\link{blockGrid}} to define grids to use in the context
of block processing of array-like objects.
\item \link{block_processing} for more information about block processing
of an array-like object.
\item \link{DelayedArray} objects.
\item \link[base]{array} objects in base R.
}
}
\examples{
m0 <- matrix(1:30, ncol=5)
block_dim <- c(4, 3)
viewport1 <- ArrayViewport(dim(m0), IRanges(c(3, 2), width=block_dim))
viewport1
block1 <- read_block(m0, viewport1)
block1
## No-op:
write_block(m0, viewport1, block1)
stopifnot(identical(m0, write_block(m0, viewport1, block1)))
write_block(m0, viewport1, block1 + 100L)
viewport2 <- ArrayViewport(dim(m0), IRanges(c(1, 3), width=block_dim))
write_block(m0, viewport2, block1 + 100L)
## Using a grid:
grid0 <- RegularArrayGrid(dim(m0), spacings=c(3L, 2L))
grid0
length(grid0) # number of blocks defined by the grid
read_block(m0, grid0[[3L]]) # read 3rd block
read_block(m0, grid0[[1L, 3L]])
## Walk on the grid, colum by column:
m1 <- m0
for (b in seq_along(grid0)) {
viewport <- grid0[[b]]
block <- read_block(m1, viewport)
block <- b * 1000L + block
m1 <- write_block(m1, viewport, block)
}
m1
## Walk on the grid, row by row:
m2 <- m0
for (i in seq_len(dim(grid0)[[1]])) {
for (j in seq_len(dim(grid0)[[2]])) {
viewport <- grid0[[i, j]]
block <- read_block(m2, viewport)
block <- (i * 10L + j) * 1000L + block
m2 <- write_block(m2, viewport, block)
}
}
m2
}
\keyword{methods}
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