x0=0.7;
l=[];
skip=400;
n=1000;
for a=2.9:0.01:4
f = @(x) a.*x.*(1-x);
df=@(x)a.*(1-2*x);
x=[x0];
for k=1:n 
    x=[x,f(x(end))];
end;
figure(1)
hold on
plot(a.*ones(1,n-skip+1),x(skip+1:n+1),'r.','MarkerSize',0.5)
l=[l,sum(log(abs(df(x(skip+1:n+1)))))/(n-skip+1)];
end
figure(2)
plot(2.9:0.01:4,l,'b-')