function arnoldi()
A=rand(20);
v(:,1)=[1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]';
m = input('請輸入m:');

for j=1:m
      s(1:20,j)=[0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0]';
      for i=1:j
        h(i,j)=v(:,i)'*A*v(:,j);
        s(1:20,j)=s(1:20,j)+h(i,j)*v(:,i);
      end    
        bav(:,j+1)=A*v(:,j)-s(1:20,j);
        h(j+1,j)=norm(bav(:,j+1));
        v(:,j+1)=bav(:,j+1)/h(j+1,j);
end
h(1:m,1:m)
eig(h(1:m,1:m))
ta(:,1)=eig(A)
t=eig(h(1:m,1:m));
x=real(ta); 
y=imag(ta);
x1=real(t);
y1=imag(t);
plot(x,y,'k*',x1,y1,'b*')
xlabel('特征值');
ylabel('圖像');
title('A與Hm的特征值比較');
axis([-8,15,-2,2]);
    legend('A的特征值','Hm的特征值');