Arrays in R

The function aperm(a, perm) may be used to permute an array, a. The argument perm must be a permutation of the integers {1, …, k}, where k is the number of subscripts in a. The result of the function is an array of the same size as a but with old dimension given by perm[j] becoming the new j-th dimension. The easiest way to think of this operation is as a generalization of transposition for matrices. Indeed if A is a matrix, (that is, a doubly subscripted array) then B given by

> B <- aperm(A, c(2,1))

is just the transpose of A. For this special case a simpler function t() is available, so we could have used B <- t(A).