function basinHenon(num)
%finds the basin of attraction for the Henon attractor
xmin=-8.0;
xmax=8.0;
ymin=-11.0;
ymax=5.0;
escape = 20.0;
tmax = 20;
dx=(xmax-xmin)/(num-1);
dy=(ymax-ymin)/(num-1);
Boxes=zeros(num);
for i=1:num,
	for j=1:num,
		x=xmin+(i-1)*dx;
		y=ymax -(j-1)*dy;
		for t=1:tmax,
			[x,y]=henon(x,y);
			if abs(y) > escape
				break;
			end
		end
		if(t ~= tmax)      %leave 0 for trapped set
			Boxes(j,i)=t;  % For image the order is y,x, with (1,1) at top left
		end
	end
end
xvect = linspace(xmin,xmax,num);
yvect = linspace(ymax,ymin,num);

bmax = max(max(Boxes))
Boxes = (Boxes)*100/bmax;   % scale to range 100 elements in default color map
image(xvect,yvect, Boxes);  % plot the matrix as an image & scale to colormap
colormap(hot);
map = colormap;
mapnew = flipud(map);
mapnew(1,1)=0; mapnew(1,2)=0; mapnew(1,3)=0;
colormap(mapnew);
colorbar;
axis xy                     % reverse the y axis to normal
hold on
iterate(1,1,1000)           %plot the attractor too
hold off