How to find out if a matrix is singular? [duplicate]

Answer 1

I would use cond. This gives you a numerical estimate of how close to singular a matrix is (where Inf is a singular matrix).

For example:

m = randn(4);
cond(m)   %Well conditioned, usually in the 10's

m = diag([1e-6 1 2 1e6]);
cond(m)   %Less well conditioned, 1e12

m = diag([0 1 2 3]);
cond(m)   %Singular:  Inf