clf
theta=linspace(0,2*pi,100);
x=cos(theta); y=sin(theta);
hbead=line(x(1),y(1),'marker','o','markersize',8,'erase','xor');
axis([-1 1 -1 1]);
axis('square');
for k=2:length(theta)
    set(hbead,'xdata',x(k),'ydata',y(k));
    drawnow
    pause(.1)
end