Question

Hello there.
Given A = {1,2,3,4} and B = {x,y,z}
Let R:A->B | R = {(1,y),(1,z),(3,y),(4,x),(4,z)}

I understand all this terminology.
Where I am stuck is when I am asked to determine the matrix of a relation. No luck on Googleing the topic either.

Thanks in advance.