Negative index of matrix

I want to implement this code but I am unable to do so...

for m = 3:-1:-3
    for n = 3:-1:-3
            Y( m,n) = G(center_index + (m-n))  +  (-1i*m*w*C(center_index  + (m-n)));
end
end

G and C are vectors.

Can someone please help?

Answer 1

[Alan Stevens]

Like this

m = 3:-1:-3;
n = 3:-1:-3;

for i = 1:numel(m)
    for j = 1:numel(n)
            Y( i,j) = G(center_index + (m(i)-n(j)))  +  (-1i*m(i)*w*C(center_index  + (m(i)-n(j))));
end
end

[Prabhav Manchanda]

Thank you!