permutedims!

permutedims!(dest, src, perm)

Permute the dimensions of array src and store the result in the array dest. perm is a vector specifying a permutation of length ndims(src). The preallocated array dest should have size(dest) == size(src)[perm] and is completely overwritten. No in-place permutation is supported and unexpected results will happen if src and dest have overlapping memory regions.

Examples

Permute dimensions of a matrix:

julia> A = [1 2 3; 4 5 6; 7 8 9];
julia> B = similar(A, (3, 3));
julia> permutedims!(B, A, (2, 1))
3×3 Array{Int64,2}:
1  4  7
2  5  8
3  6  9

This example permutes the dimensions of matrix A using the permutation (2, 1) and stores the result in matrix B.

Permute dimensions of a 3D array:

julia> C = rand(1:9, (2, 3, 4));
julia> D = similar(C, (3, 2, 4));
julia> permutedims!(D, C, (3, 2, 1))
3×2×4 Array{Int64,3}:
[:, :, 1] =
2  5
9  3
6  7

[:, :, 2] =
4  6
8  9
1  2

[:, :, 3] =
3  1
2  4
5  8

[:, :, 4] =
7  3
5  6
9  1

This example permutes the dimensions of a 3D array C using the permutation (3, 2, 1) and stores the result in array D.

Common mistake example:

julia> X = [1 2 3];
julia> Y = [1 2 3];
julia> permutedims!(X, Y, (1, 2))
ERROR: MethodError: no method matching permutedims!(::Array{Int64,2}, ::Array{Int64,2}, ::Tuple{Int64,Int64})

In this example, the function is called with X and Y as arguments, but X is not a preallocated array. It's important to ensure that the destination array (dest) is preallocated and has the correct size before using permutedims!.

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permutedims!

Examples

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