col=150;
m=300;
cx=0;
cy=0;
l=0.01;
x=linspace(cx-l,cx+l,m);
y=linspace(cy-l,cy+l,m);
[X,Y]=meshgrid(x,y);
Z=X +i*Y;
c=-0.5-i*0.8660254;
for k=1:col;
Z=2/3*Z + 1/3*1./(eps+Z.^2);
end
W=abs(Z-c);
A=angle(Z);
colormap prism(256);
pcolor(W-A);
shading flat;
axis('square','equal','off');

