H_householder.m

function [H,UL,UR]=H_householder(A)
% household 约化，约化一般实矩阵为上海森伯格矩阵,约化对称矩阵A为对称三对角矩阵
[m,n]=size(A);UR=eye(n);
%Ak=zeros(n0,n0);
   for j=1:n-2 
      sigma=sign(A(j+1,j))*norm(A(j+1:n,j),2);
      u=A(j+1:n,j)+sigma*eye(n-j,1);
      beta=sigma*(sigma+A(j+1,j));
      I=eye(n-j);
      Rj=I-1/beta*(u*u');
      Uk=blkdiag(eye(j),Rj);
      A=Uk*A*Uk;
      UR=UR*Uk;
   end
      H=A;%Uk=H;
      UL=UR';