shg     %show graph 
clf     %clear plotting window
n=1;    %index
x=0;

set (gcf,'doublebuffer','on')
y=1;
h=plot(n,y,'.');
axis([-1 1 -1 1])
axis square
stop=uicontrol('style','toggle','string','stop');

while get(stop,'value')==0
    y=cos(n/200);
    set(h,'xdata',x,'ydata',y);
    drawnow;
    n=n+1; 
end