Subtracting Matrices of Different Sizes by subtracting A(1) from all of B for all of A

Hello,

I have been reading a lot about sbxfun, and it ALMOST does what I want it to do.

Let's say I have two matrices

A = [1 2 3
     4 5 6
     7 8 9];

B = [1  2  3  4
     5  6  7  8
     9  10 11 12];

I want to take A(1,1) and subtract it from EVERY element in B and store this in C. Then I want to move on to A(1,2) and subtract it from EVERY element in B and store this in C. In the end I would get (if I used A(1,1) and A(1,2) to subtract from B):

C(:,:,1) = [0  1  2  3
            4  5  6  7  
            8  9  10 11];

C(:,:,2) = [-1  0  1  2
             3  4  5  6
             7  8  9  10];

etc...

I have tried sbxfun by adding some zeros to A to make it the same size as B, reshaping A into a 3d matrix and then sbxfun(@minus)-ing the now two equal size matrices, but this only takes row 1 of A and subtracts it from rows 1, 2, and 3 of B. It does not subtract EACH element of row 1 of A from EACH element of B.

I currently use a for loop to do this, but it take up a lot of computing power to do this, as my matrices are quite large. Is there a function that would do this for me and speed things up?

Thanks ahead of time.

Answer 1

[Azzi Abdelmalek]

A = [1 2 3
   4 5 6
   7 8 9];
B = [1  2  3  4
   5  6  7  8
   9  10 11 12]
D=A'
C=bsxfun(@minus, B,reshape(D(:),1,1,[]))

[Joe]

OK thank you let me check this out with my code

[Joe]

Thank you Azzi you totally killed it and are a gentleman and a scholar. Works perfectly.