MATLAB: Converting 4D matrix to 2D with multiple for-loop

bxsfunfor loop

Hello, I'm trying to convert 4D matrix to 2D matrix instead of for-loop.
Here is my code.
X = randi(10,100,10,100);
A = ones*(10,100);
SUM = zeros(10,100);
for k=1:10
    for l=1:100
        for m=1:10
            for n=1:100
                SUM(m,n) = SUM(m,n) + A(k,l) * X(k,l,m,n);
            end
        end
    end
end
I want to know how to change 4D to 2D for simpler calculation without for-loops. Thank you.

Best Answer

X = randi(100,10,100,10,100);
A = randi(20,10,100);
[k,l,m,n] = size(X);
z = bsxfun(@times,X,A);
out = reshape(sum(reshape(z,k*l,1,m,n),1),m,n);
or
out = squeeze(sum(reshape(z,k*l,1,m,n)));
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