function henonlp
Zmax=[];
Zmin=[];
for p=linspace(0,1.4,300);
    x=[1;0;p;.3];
    e=[1 0
       0 1];
    lp=0;
    for k=1:500
        x=Henon(x);
        J=[-2*p*x(1) 1
            .3       0];
        e=GS(J*e);
        mod(1)=norm(e(:,1));
        mod(2)=norm(e(:,2));
        lp = lp+log(abs(mod));
        e(:,1)=e(:,1)/mod(1);
        e(:,2)=e(:,2)/mod(2);
    end
    lp=lp/500;
    Zmax=[Zmax lp(1)];
    Zmin=[Zmin lp(2)];
 end
p=linspace(0,1.4,300);
plot(p,Zmax,'-',p,Zmin,'-');
title('Lyapunov exponents of Henon')
xlabel('parameter p'),ylabel('lyapunov exponents')
grid on