%stabregionsExplicit
clear;clf
% grid in complex plane
range=4;h=0.05;
R = -range:h:range;
I = -range:h:range;
% corresponding z values on grid
[x,y]=meshgrid(R,I);
z=x+1i*y;
for i=4:-1:1
  tmp=0*z;
  for k=1:i
    tmp = tmp + z.^k/(gamma(k+1));
  end
  G = abs(1+tmp);
  contour(R,I,G,[1 1],'r')
  if i==4,axis square;hold on;end
end
grid
