MATLAB: How to multiplay matrices in different dimensions

Question

I would like to multiply a 3D matrice with a 2D matrice.

Answer 1

Perhaps:

a = rand(2,2,3);
b = [2, 2; 4, 4]
% Elementwise - auto-expanding since R2016b:
r = a .* b
% Matrix multiplication:
r = zeros(2, 2, 3);
for k = 1:3
    r(:, :, k) = a(:, :, k) * b;
end

If the later is wanted, you can vectorize the code or use some tools from the FileExchange to avoid the loop.