I'm trying to make a 2D contour plot of a function with a complex input and a real output, namely: $f(z=x+iy)= |z^2-3z|$, on MATLAB. I want to make a contour plot of f, such that the axes are $(x,y)$, i.e. $(\Re(z),\Im(z))$.
How is this done in MATLAB? The problem I'm having is the fact the input is complex.