How to create a custom matrix?

I want to create a matrix that look like this:

The first n rows are all 0. The second n rows are calculated separately by some operation like:

W * V

Where W is a diagonal (n * n) matrix and V is an (n * 3) matrix.

How can I do this?

Answer 1

[Rik]

This is a simple contatenation:

n=8;
%generate W and V
W=randi(20,n,n);
V=randi(5,n,3);

output=[zeros(n,3) ; W*V];