Quick way to change complex number into NaN

If I have a matrix of A=[1 2 ; 2+i 3] I want to make it into A=[1 2; NaN 3] Is there anyway like using isnan function to do this? Thanx!

Answer 1

[Teja Muppirala]

A(imag(A)~=0) = nan;

[Qian]

Thanx!