function X2=henon(X1)%HENON   Henon map (a 2nd-order discrete system)%%             x(n+1) = 1 - a*x(n)^2 + y(n)%             y(n+1) = b*x(n)%%        In this demo, a = 1.4, b = 0.3, %        Initial conditions: x(0) = 0, y(0) = 0%        Reference values are:  LE1 = 0.418, LE2 = -1.621, LD = 1.26%%        The reference values are from the following references:%%        [1] A. Wolf, J. B. Swift, H. L. Swinney and J. A. Vastano,%           "Determining Lyapunov Exponents from a Time Series,"%            Physica D, Vol. 16, pp. 285-317, 1985.%%        [2] Keith Briggs, "An Improved Method for Estimating Liapunov%            Exponents of Chaotic Time Series," Phys. Lett. A, Vol. 151,%            pp. 27-32, Nov. 1990.%        by Steve Wai Kam SIU, Jun. 29, 1998.%Parametersa=1.4;b=0.3;%Rearrange input data in desired format%Note: the input data is a column vectorx=X1(1);y=X1(2);Q=[X1(3),X1(5);   X1(4),X1(6)];%Henon mapX=1-a*(x^2)+y;Y=b*x;%Linearized systemJ=[-2*a*x, 1;        b, 0];%Variational equationF=J*Q;%Output dataX2=[X; Y; F(:)];