"Halley" wrote in message <j7pdmt$3o9$1@newscl01ah.mathworks.com>... > > %Calculate old values > rho(i) = (x_a(i,:).*A.*x(:,i))./(x_a(i,:).*B.*x(:,i)) ========

I suspect you mean to do * instead of .*

In any case, the sizes definitely aren't compatible for the .* operation