a=[0 .2 -.15 .85];
b=[0 -.26 .28 .04];
c=[0 .23 .26 -.04];
d=[.16 .22 .24 .85];
e=[0 0 0 0];
f=[0 1.6 .44 1.6];
pk=[.01 .07 .07 .85];
pt=sum(pk);
p=cumsum(pk);
xscale=25;
yscale=22;
xoffset=100;
yoffset=20;
x=0;
y=0;
for ii=1:2
 pk=rand(1);
 if pk<= p(1) 
   k=1;
 elseif pk<=p(2) 
   k=2;
 elseif pk<=p(3) 
   k=3;
 else
   k=4;
 end
 newx=a(k)*x+b(k)*y +e(k);
 newy=c(k)*x+d(k)*y +f(k);
 x=newx;
 y=newy;
end
%figure('Position',[0 0 300 400])
figure('Position',[0 0 660 880])
axis([0 200 0 250])
hold on
q=plot((x*xscale+xoffset),(y*yscale+yoffset),'EraseMode','none','Color','green')
while 1
 pk=rand(1);
 if pk<= p(1) 
   k=1;
 elseif pk<=p(2) 
   k=2;
 elseif pk<=p(3) 
   k=3;
 else
   k=4;
 end
 newx=a(k)*x+b(k)*y +e(k);
 newy=c(k)*x+d(k)*y +f(k);
 x=newx;
 y=newy;
 set(q,'XData',(x*xscale+xoffset),'YData',(y*yscale+yoffset))
 drawnow
end