[Matplotlib-users] Plotting filled circles

[Andrew M. <and...@an...>]

I'm a new user of matplotlib (athough I have been using both Matlab and
Python for years).

I have an application where I need to display data as a set of filled
circles. The centre and the radius of the circles are both specified in
data coordinates. The data points have an additional scalar attribute,
which is displayed using a pseudo-colour mapping.

I've hacked something together where the circles are approximated by
polygons using either the axis fill method or the pylab fill function. I
select the colour by calling the get_rgba method of a ScalarMappable
object. In the following code snippet c is a tuple containg the x and y
coords of the centre of the circle, the radius, and a scalar "value"

theta = arange(numSegs+1) * 2.0 * math.pi / numSegs
cos_theta = cos(theta)
sin_theta = sin(theta)
for c in cart:
    x = c[1] + c[3] * cos_theta
    y = c[2] + c[3] * sin_theta
    v = c[4]
    fill(x, y, facecolor=mapper.to_rgba(v), linewidth=0.5)

It all works. However, I saw in the API documentation (and the source)
that there is a Circle object in patch. I was hoping that using this
rather than polygons would give better quality output and possibly
smaller files. Now I can instantiate it

        circle = Circle((x,y), c[3], facecolor=cmapper.to_rgba(v))

but can't work out what to do with it! I've tried

        ax.add_patch( circle )

and also

        trans = blend_xy_sep_transform( ax.transAxes, ax.transData  )
        circle.set_transform( trans )
        ax.add_patch( circle )

Neither work. Any ideas?

Regards,

Andrew