R: Split Array/Matrix By Its Margins

asplit {base}

R Documentation

Split Array/Matrix By Its Margins

Description

Split an array or matrix by its margins.

Usage

asplit(x, MARGIN)

Arguments

`x`	an array, including a matrix.
`MARGIN`	a vector giving the margins to split by. E.g., for a matrix `1` indicates rows, `2` indicates columns, `c(1, 2)` indicates rows and columns. Where `x` has named dimnames, it can be a character vector selecting dimension names.

Details

Since R 4.1.0, one can also obtain the splits (less efficiently) using apply(x, MARGIN, identity, simplify = FALSE). The values of the splits can also be obtained (less efficiently) by split(x, slice.index(x, MARGIN)).

Value

A “list array” with dimension dv and each element an array of dimension de and dimnames preserved as available, where dv and de are, respectively, the dimensions of x included and not included in MARGIN.

Examples

## A 3-dimensional array of dimension 2 x 3 x 4:
d <- 2 : 4
x <- array(seq_len(prod(d)), d)
x
## Splitting by margin 2 gives a 1-d list array of length 3
## consisting of 2 x 4 arrays:
asplit(x, 2)
## Splitting by margins 1 and 2 gives a 2 x 3 list array
## consisting of 1-d arrays of length 4:
asplit(x, c(1, 2))
## Compare to
split(x, slice.index(x, c(1, 2)))

## A 2 x 3 matrix:
(x <- matrix(1 : 6, 2, 3))
## To split x by its rows, one can use
asplit(x, 1)
## or less efficiently
split(x, slice.index(x, 1))
split(x, row(x))

[Package base version 4.4.1 Index]