clf()
theta=linspace(0,2*pi,1000)
x=cos(theta)
y=sin(theta)
hbead=plot(x[1],y[1],'o')
htrail=plot(x[1],y[1],'.')
axis([-1,1,-1,1])
for i in range(2,size(theta)):
    set(hbead)
    set(htrail)
    plot(x[1],y[1],'o')
    plot(x[1],y[1],'.')
show()