function fern
 shg
 clf reset
 set(gcf,'color','white','menubar','none','numbertitle','off','name','Fractal Fern')
 x=[.5;.5];
 h=plot(x(1),x(2),'.');
 darkgreen=[0 2/3 0];
 set(h,'markersize',1,'color',darkgreen,'erasemode','none');
 axis([-3 3 0 10])
 axis off
 stop=uicontrol('style','toggle','string','stop','background','white');
 drawnow
 p=[.85 .92 .99 1.00];
 A1=[.85 .04;-.04 .85];b1=[0;1.6];
 A2=[.02 -.26;.23 .22];b2=[0;1.6];
 A3=[-.15 .28;.26 .24];b3=[0;.44];
 A4=[0 0;0 .16];
 cnt=1;
 tic
 while ~get(stop,'value')
     r=rand;
     if r<p(1)
         x=A1*x+b1;
     elseif r<p(2)
         x=A2*x+b2;
     elseif r<p(3)
         x=A3*x+b3;
     else
         x=A4*x;
     end
     set(h,'xdata',x(1),'ydata',x(2));
     cnt=cnt+1;
     drawnow
 end
 t=toc;
 s=sprintf('%8.0f points in %6.3f seconds',cnt,t);
 text(-1.5,-0.5,s,'fontweight','bold');
 set(stop,'style','pushbutton','string','close','callback','close(gcf)')