how can plot complex data in matlab?

hi all how can I plot abs(z)<.5? I want to have an image like below. it is for abs(z)=2. thanks

Answer 1

[Azzi Abdelmalek]

alpha=-pi:0.01:pi
k=.5
x=k*cos(alpha);
y=k*sin(alpha);
fill(x,y,'r')

[sara]

thanks dear Azzi Abdelmalek. and Is there any way for abs(z)>.5.

for example if I want to got the ROC in below how can I plot this?

I mean that how can I get intersection of regions? can you guide me please?