How to copy and paste a small matrix into a bigger matrix without for-loop

For example, we have a small matrix

B = [5 2, 3 4] 

and the bigger one

A = [1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 1] 

Now I want paste B into A so that A looks like

A = [1 0 0 0 0 0 1 0 0 0 0 0 1 0 0 0 0 0 5 2 0 0 0 3 4] 

That means the values of A of the bottom right has been replaced. I would like to do this without using a for-loop. How is that possible?

PS:

1. A is always an eye(n) matrix (n is a constant).
2. B is a square matrix and has a variable size but is always less or equal to A

1 Answer

Find the relevant row and column subscripts of A and put B there.

A(end-size(B,1)+1:end, end-size(B,2)+1:end)=B 

It works even if B is not a square matrix.