Re: [Matplotlib-users] Drawing Error Ellipses

[Tinne De L. <tin...@me...>]

On Wed, Oct 28, 2009 at 9:06 AM, Eero Nevalainen
<eer...@in...> wrote:
> Hi,
>
> I need to draw error ellipses on a scatterplot. I'm guessing someone has
> done this before.
>
> I've found some examples, such as this one
> http://matplotlib.sourceforge.net/examples/pylab_examples/ellipse_rotated.html
>
> That led to the artist tutorial, and... ARGH! INFORMATION OVERFLOW!
>
> Can someone explain to me, why I suddenly have to know so much about
> matplotlib's internals to get an ellipse drawn?

Hi,

I just made a function to draw uncertainty ellipses defined by a
covariance matrix P:

def plotEllipse(pos,P,edge,face):
    U, s , Vh = svd(P)
    orient = math.atan2(U[1,0],U[0,0])
    ellipsePlot = Ellipse(xy=pos, width=math.sqrt(s[0]),
height=math.sqrt(s[1]), angle=orient,facecolor=face, edgecolor=edge)
    ax = gca()
    ax.add_patch(ellipsePlot);
    show()
    return ellipsePlot

To use it: ellipsePlot=plotEllipse([x,y],P,'black','0.3')

Hope this helps,

Tinne