MATLAB: How to create a matrix from multiples of submatrice

Question

I would like to find a smarter way of building a larger matrix from vectors. The following code works fine:

rv = [1 2 3 4];
alpha =[0.0140;
    0.0100;
    0.0100;
    0.0100];
c = [];
for i = 1:4
    c = [c; diag(alpha).*rv(i)];
end
>> c =
    0.0140         0         0         0
         0    0.0100         0         0
         0         0    0.0100         0
         0         0         0    0.0100
    0.0280         0         0         0
         0    0.0200         0         0
         0         0    0.0200         0
         0         0         0    0.0200
    0.0420         0         0         0
         0    0.0300         0         0
         0         0    0.0300         0
         0         0         0    0.0300
    0.0560         0         0         0
         0    0.0400         0         0
         0         0    0.0400         0
         0         0         0    0.0400

Essentially I build a submatrix from a vector. Then I multiple the diagonal submatrix with each element of a vector. Then I concatenate these vertically.

Is there a computationally more efficient way of doing this?

Thanks!

Answer 1

Z = reshape(rv,1,1,[]) .* diag(Alpha);
Wanted = reshape(Z,numel(rv),[]).'