matrix divide in an array or 2d matrix.

I have a matrix that is 10000x10000x15. I need to divide each element in the first two dimension by a matrix that is 3x15. I could do this in a loop, i.e.

mat = rand(10000,10000,15);
submat = rand(3,15);
newmat = zeros(10000,10000,3);

for i =1:10000
    for j = 1:10000
        newmat(i,j,1:3)=reshape(mat(i,j,1:15),1,15)/submat;
    end
end

but that would take a long time. Is there a better way to accomplish this that can do the division on the matrix as a whole?

Answer 1

[Sean de Wolski]

You can do the whole divide at once, using n instead of 10000 to avoid killing my laptop:

mat2 = reshape(mat,n^2,15);
nm2 = mat2/submat;
nm2 = reshape(nm2,n,n,3);

% Check equality
isequal(nm2,newmat)
 ans =
   1

[Victor]

Perfect. Thanks, Sean.