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

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Joe
Joe 2014-8-7
评论： Joe 2014-8-7
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.

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Azzi Abdelmalek
Azzi Abdelmalek 2014-8-7
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,[]))

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