How to save indices of a certain region of a matrix

I have a matrix, let's say A

A = [1 2 3 4; 5 6 7 8; 9 10 11 12; 13 14 15 16];

I have another matrix, let's say B

B = A(3:end,3:end);

This is how I can simple save B. But instead of saving the values of B. I want to save the indices of B that were in A.

Indices of B in A are 11,12,15 and 16.

How can I do it by using some matlab command?

Answer 1

[M]

I am not sure if I understood your question but here is a second simple example:

A = [10 11 12;13 14 15; 16 17 18];
B = [14 15; 17 18];

You can see that B is member of A:

idx = ismember(A,B)
  idx =
  3×3 logical array
   0   0   0
   0   1   1
   0   1   1

And you can get the indices of B in A:

find(idx)
    ans =
     5
     6
     8
     9

Answer 2

[Bhaskar R]

ind = find(ismember(A(:), B(:)))

[Ahmad Hasnain]

Thanks, both the answers solved my problem.