clf
theta=linspace(0,2*pi,1000); %creates theta vector
x=cos(theta);y=sin(theta);   %creates x and y coordinates
hbead=line(x(1),y(1),'marker','o',...   
  'markersize',15,'erase','xor','color','k'); %initial bead and gets handle
htrail=line(x(1),y(1),'marker','.','color','r','erase','none');
axis([-1 1 -1 1]);axis('square');
for k=2:length(theta)
  set(hbead,'xdata',x(k),'ydata',y(k)); %cycle thru all positions
  set(htrail,'xdata',x(k),'ydata',y(k)); %cycle thru all positions
  drawnow  % redraw
end