MATLAB: Efficient code writing…

efficient writingmatrix multiplication

Hi all. First time posting here, hope I can get some nice ideas. I have 3 large matrices (of equal size), representing the x,y and z coordinates of points. So say my matrices are 200 by 200, it means they are representing 200×200 points. Now, I want to apply this transformation matrix to each point, so that I get some linear combination of the point being transformed. Of course, I know I could opt for a loop where I update the indices of my matrices and each time apply the transformation. But I'd like to know how I can do this more efficiently… I know matlab works better using vectorisation, so I am thinking along the lines of using structures or something… Any ideas?
Thanks. Dan

Best Answer

variant
C = cat(3,x, y, z);
s = size(C);
Cout = permute(reshape(M*reshape(permute(C,[3 2 1]),s(3),[]),s(3),s(2),[]),[3 2 1]);
variant 2
Cout2 = C;
for i1 = 1:size(C,2)
    Cout2(:,i1,:) = (M*squeeze(C(:,i1,:)).').';
end
Related Question