Which version of matplotlib are you using? Also, do you have an example dataset and a simple, self-contained example to demonstrate this?

Chances are, there are NaNs occurring in the calculation, but since we have code elsewhere that handles NaNs properly, it probably isn't impacting your graph. However, it *might* be a sign that there is something wrong/unexpected with your input data (or maybe even the contour levels themselves).

Cheers!
Ben Root



On Tue, Jun 17, 2014 at 6:45 AM, <keith.briggs@bt.com> wrote:
Using pyplot.contour, I'm getting

/usr/lib/pymodules/python2.7/matplotlib/contour.py:374: RuntimeWarning: invalid value encountered in true_divide
  dist = np.add.reduce(([(abs(s)[i]/L[i]) for i in range(xsize)]),-1)

although the resulting plot seems to be ok.

Keith



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