MATLAB: How to multiply 4D array.

arraysMATLABmatrix array

i want to multiply
L(:,:,k,:).*M(:,:,k,:);
i want to multiply without loop.

Best Answer

You could try downloading the tensor toolbox by Kolda and Bader, where this is provided as a command ttt(L, M, 3, 3). Alternatively, you can use the following code:
permL = permute(L, [3 1 2 4]);
permM = permute(M, [3 1 2 4]);
szL = size(L);
szM = size(M);
result = permL(:, :)'*permM(:, :);
result = reshape(result, [szL([1 2 4]), szM([1 2 4])]);
This returns a 6-dimensional array result, such that
result(i1, i2, i3, j1, j2, j3)
is the same as
a = 0; for k=1:size(L, 3), a = a + L(i1, i2, k, i3)*M(j1, j2, k, j3); end; a
Is this what you wanted to compute?
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