I am working with matplotlib in Python 3.3. I have an animated 2d and 3d window, on which I draw points. These points represent objects, but it is not certain that they are actually there. So I want to draw a circle around these points to display the uncertainty. This uncertainty is variating, so bottomline: I want to draw multiple (might be 0, might be 100) circkles in a 2D animation with a variable center and a variable radius.

I tried scatter. Scatter looks very promising, until I resize the screen: the size of the scatter is in pixels and not related to the size of the axes. Any idea how I can do this?

I have tried the following scatter code:

```
#In the init
self.circles = self.ax.scatter([],[],[],c = 'b',alpha=0.6)
#In the animate function
self.circles.set_offsets([[10],[15]])    
self.circles._sizes = [2000]

```

The centerpoint is correct, at x = 10 and y = 15. But the size is the size in pixels and not related to the axes. In this case I expected the circle to hit x = 10 and y = 20015, for example. But it does not. 

This becomes a problem when I resize the window.