Gerschgorin's disk Thm (a test)

plot eigenvalue on complex plane show that all these points located in such circles.

% ------------------------------------------------------
% 4-1
% test for Gerschgorin's disk Thm with A a C(m*m) matrix
% ex : >>testGerschgorin(A) ;
% % plot eigenvalues in redx located in these circles
% note : you could use this without input A as a demo
% ------------------------------------------------------
% Summit.Suen(at)NTUMath
% [e-mail]
% 14.May.2007
% 17.May.2007 revised