Matrix_invpow2.m

function [u_normal,lambta]=Matrix_invpow2(A,p,u)
% 反幂法计算矩阵最小特征值（指定值附近特征值）及相应特征向量+原点平移

      [m,n]=size(A);I=eye(n);
      B=A-p*I;

      i=1;dellab=1;miu(1)=max(u);
while abs(dellab)>1e-6
      u_normal(i,:)=[i-1,u'];
      v=B\u;
      i=i+1;
      [vmax,j]=max(abs(v));miu(i)=vmax*sign(v(j));
      u=v/miu(i);
      dellab=miu(i)-miu(i-1);
end
      lambta=1./miu+p;