MATLAB: How to subtract elements in a matrix

Question

Hello,

I have a matrix and I need to subtract every element from each other in each row. So, for example, if I have a matrix A=[1 2 3; 4 8 9] the result should be for example this B=[1 2 1; 4 5 1] – the sequence is not important. But I need to know that the result in the matrix B corresponds to a particular elements' subtraction in matrix A. So if I have for example a subtraction of 2-1, which is A(1,2)-A(1,1) in matrix A and the result is 1 in matrix B I need to know that 1 corresponds to A(1,2)-A(1,1) and keep track of it.

I have tried to do it with cycles and also with a "bsxfun" function but unfortunately can't get the correct result.

g=[1 3 8; 4 6 2];
[u,v]=size(g);
      for i=1:u
          for j=1:v
      a(i,j)=bsxfun(@minus,g(i,j),g(i,j)');
          end
      end

I'll be glad if anyone can help me. Thanks

Answer 1

You don't need a for-loop.

C = nchoosek(1:size(A,2),2);
B = A(:,C(:,2))-A(:,C(:,1));