Matrix operations

i have an n by i matrix call it B. I want to apply two different operations to B. I want to perform the first operation on elements of B<0 and then perform the other operation to the rest of B. The operations themselves are n by n matrices. How do i do it please?

Answer 1

[Titus Edelhofer]

Hi,

use logical indexing:

idx = B<0;

% operate on these indices:
B(idx) = ...;
% and now on those >= 0:
B(~idx) = ...;

Titus