Norm of A = [2 3; 1 -1] not equal to sqrt(15)

Let A = [2 3; 1 -1].

norm(A) gives 3.6180 but shouldn't it equal sqrt(15) ~= 3.8730?

Any idea why it is like this?

Answer 1

[Torsten]

norm(A)=sqrt(maximum eigenvalue of A'*A)

You want norm(A,'fro'), I guess.

Best wishes

Torsten.

[Robin Lindström]

Thank you very much! :)