func12.m

数值分析最常用的四十种算法

%func12.m
%Find eigenvalue,using QR methom
m=[5,-3,2;6,-4,4;4,-4,5]
maxtimes=1000
a=m
start=now
for i=1:maxtimes
   [Q,R]=qr(a)
   b=a
   a=R*Q
   if (abs(norm(a,inf)-norm(b,inf))<1e-4)
       disp('iteration times:')
       disp(i)
       break
   end
end
finish=now
disp('Elapse time:')
disp(finish-start)
  
%a =

%    2.9999   -1.0001  -12.0002
%   -0.0001    2.0001   -1.9989
%    0.0000   -0.0000    1.0000

%iteration times:
%    22
%Elapse time:
% 0.090s