how to assign part of a matrix to other matrix in matlab

Question

I have a 30 x 30 matrix, called A, and I want to assign B as the leftmost 30 x 20 block of A how can I do that?

Is this the correct way to do i

Answer 1

A_new = A(:,1:20)

takes all the rows from A with this part A(:,) and the first 20 columns with this part A(,1:20)

A_newis now 30x20

You can also iterate over elements in two loops, but the above answer is easiest