function henonorb(y,y1,d,iter,e,j)
%y=yposition y1=velocity,d=time step
%iter=iterations, e=energy, j=1 live motion
%e.g. e=1/12; e=1/8; or e=1/6;
%p=.205; q=.265; r=.05; s=200;
%henonorb(p,q,r,100*s,e,0);
clf
hold on
if (j==1)
    set(gca,'nextplot','replacechildren');
end
x=0;
x1=real(sqrt(2*e-y1*y1-y*y+2*y*y*y/3));
for i=1:iter
    xh=x;
    x2=-x - 2 * x * y;
    y2=-y - x * x + y * y;
    x1=x1 + x2 * d;
    y1=y1 + y2 * d;
    xx=x + x1 * d;
    yy=y + y1 * d;
    line([x xx],[y yy]);
    x=xx; y=yy;
    if (j==1)
        F(i) = getframe;
    end
end
%movie(F,1);
hold off