Removing data from graph?


I'm trying to create an image on screen, and update it with new data. It
works to have the data added, but my images keep showing the old data.

I'm plotting sin(x) through the time, and every .5 seconds, I redraw the
    a = figure.add_subplot(111)
    t = arange(low,upper,0.01)
    s = sin(2*pi*t)

This is called first with low=0, upper=5, then with low=1, upper=6 etc.
What I want is to see only 5 seconds, with the data moving off on the left
side. However, what I see is that the old data is retained, and the sine is
squeezed more and more.

Does anyone know how to change this?

Chris Niekel