function gershcircles(A)
%GERSHCIRCLES plots the Gershgorin circles
%  GERSHCIRCLES(A) draws the Gershgorin circles for
%   the square matrix A and its transpose.
n = size(A);
if n(1) ~= n(2)
  error('Only square matrices');
else
  n = n(1); circler = zeros(n,201); circlec = circler;
end
center = diag(A);
radiic = sum(abs(A-diag(center)));
radiir = sum(abs(A'-diag(center)));
one = ones(1,201); cosisin = exp(i*[0:pi/100:2*pi]);
figure(1); title('Row circles');
xlabel('Re'); ylabel('Im');
figure(2); title('Column circles');
xlabel('Re'); ylabel('Im');
for k = 1:n
  circlec(k,:) = center(k)*one + radiic(k)*cosisin;
  circler(k,:) = center(k)*one + radiir(k)*cosisin;
  figure(1);
  patch(real(circler(k,:)),imag(circler(k,:)),'red');
  hold on
  plot(real(circler(k,:)),imag(circler(k,:)),'k-',...
     real(center(k)),imag(center(k)),'kx');
  figure(2);
  patch(real(circlec(k,:)),imag(circlec(k,:)),'green');
  hold on
  plot(real(circlec(k,:)),imag(circlec(k,:)),'k-',...
     real(center(k)),imag(center(k)),'kx');
end
for k = 1:n
  figure(1);
  plot(real(circler(k,:)),imag(circler(k,:)),'k-',...
     real(center(k)),imag(center(k)),'kx');
  figure(2);
  plot(real(circlec(k,:)),imag(circlec(k,:)),'k-',...
     real(center(k)),imag(center(k)),'kx');
end
figure(1); axis image; hold off;
figure(2); axis image; hold off
return