clear all
d0=1e-12;
A=[];Le=[];
for a=0:0.001:1.4
    x1=0;y1=0;
    x2=0;y2=d0;
    lsum=0;
    for j=1:500
        x3=a-x1*x1+0.3*y1;
        y1=x1;
        x1=x3;
        x4=a-x2*x2+0.3*y2;
        y2=x2;
        x2=x4;
        d1=sqrt((x2-x1)^2+(y2-y1)^2);
        x2=x1+(d0/d1)*(x2-x1);
        y2=y1+(d0/d1)*(y2-y1);
        if j>100
           lsum=lsum+log(d1/d0);
        end
    end
    le=lsum/(j-100);
    A=[A;a];Le=[Le;le];
end
subplot(2,1,1)
plot(A,Le,'k')
grid
hold on
b=0.3;
n=2000;
x=0;
y=0;
a=0:0.001:1.4;
   for i=1:n/100
     xprev=x;
     yprev=y;
     x=a-xprev.*xprev+b*yprev;
     y=xprev;
   end
   for i=1:n
     xprev=x;
     yprev=y;
     x=a-xprev.*xprev+b*yprev;
     y=xprev;
     if i>1990
 hold on
 subplot(2,1,2)
 plot(a,x,'k.','markersize',1);
 title('Henon Bifurcation');
   end
   end
grid