how to extract special elements from a matrix

Hi, I have a matrix, let say M1 = [1,0,0,8;0,0,15,0;0,0,0,0;7,0,0,0].

How can I extract only non-zero elements to another matrix M2.

Thank you.

Answer 1

[Andrei Bobrov]

M2 = nonzeros(M1);

Answer 2

[Walter Roberson]

M2 = M1(M1 ~= 0);