Re: [Matplotlib-users] Plotting filled circles

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

Eric Firing wrote:
> Andrew McLean wrote:
>> 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 )
>
> This works for me in the sense that I can put circles or ellipses on a 
> plot.  Note that if you are trying to do this interactively you need 
> to explicitly call draw() or draw_if_interactive() (pylab functions) 
> after the call to add_patch, because the axis methods differ from 
> pylab functions in that the latter automatically call 
> draw_if_interactive() but the former do not.
>
That was useful. Thanks. Turns out the problem was that I wasn't setting 
the axis limits. I added:

    axis([xmin, xmax, ymin, ymax])

and it all worked.
> The circle in data coordinates is a circle, however, only if you use a 
> 1:1 aspect ratio.  Does this suit your needs?  If so you can get it 
> with the pylab axis('equal') or axis('scaled') command. Or do you 
> really want to specify the radius of the circle in x-data units or in 
> y-data units?  (I have no idea what a Dorling Cartogram is.)
I was using axis('equal'). And yes this is what I want ;-). The x and y 
data units should map to the same physical scale and the radius is in 
those units.

Dorling cartograms described here (with an example near the bottom of 
the page):

http://www.ncgia.ucsb.edu/projects/Cartogram_Central/types.html

Regards,

Andrew