A=[0.05,0.85,0.05,0.25;0.45,0.05,0.45,0.25;0.45,0.05,0.05,0.25;0.05,0.05,0.45,0.25]
v=rand(4,1) //initial guess vector

for k = 1:20
    w=A*v;
    lambda=v'*w;
    v=w/norm(w);
end

v



z=poly(0,'z');

p=det(z*eye(4,4)-A);

roots(p)'

lambdaI=zeros(4,4);
for k = 1:4
    lambdaI(k,k)=v(k);
end

lambdaI
det(lambdaI-A)