Matlab Function to Compute Matrix Operations

So I want to make a function to compute the result of the following equation:

My matlab .m function file starts off with:

    function dNdt = compute(t, N, E, A)

But I am having trouble figuring out how to add up matrices...and particular rows/columns at that. I know I have to use the symsum command but mine is a little different from all the examples I've seen since I'm dealing with matrices. Any idea on how to go about this?

Answer 1

[dpb]

In Matlab the RHS is just

N.*(E+a*N)

where

size(N)=[3,1]
size(a)=[3,3]

That's taking the shortcut of not expanding the diagonal matrix the multiplication of which reduces to the element by element of the diagonal elements.