read_block {DelayedArray} | R Documentation

## 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

`x` | An array-like object.
`viewport` | An ArrayViewport object.
`block` | An ordinary array of the same dimensions as `viewport`.

### See Also

- ArrayViewport objects.

- `blockGrid` to define grids to use in the context of block processing of array-like objects.

- block_processing for more information about block processing of an array-like object.

- DelayedArray objects.

- 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

[Package DelayedArray version 0.10.0 Index]