Matlab script for a dynamical system

Question

The code

 function hennonMap(a, b, xn, yn, upper)
 Xval = zeros(upper, 1);
 Yval = zeros(upper, 1);
 for i=1:upper
Xval(i) = xn;
Yval(i) = yn;
x  = yn + 1 - a*xn^2;
y  = b * xn;
xn = x;
yn = y;
end
end

Is giving me zeros, can anyone see why?

Answer 1

Try this:

function [Xval,Yval] = hennonMap(a, b, xn, yn, upper)
Xval = zeros(upper, 1);
Yval = zeros(upper, 1);
for i=1:upper
Xval(i) = xn;
Yval(i) = yn;
x  = yn + 1 - a*xn^2;
y  = b * xn;
xn = x;
yn = y;
end
end