[Matplotlib-users] matplotlib.nxutils.pnpoly returns True for some vertexes, and False for others

[Maria L. <li...@us...>]

Hello,

I tested the following code on my Mac laptop and our production Linux server both running matplotlib V1.0.1. Both machines observe the same output from the code, so I was wondering if somebody is aware of the problem or if it's some undocumented feature of "pnpoly()" function from matplotlib.nxutils?

I use matplotlib.nxutils.pnpoly() function from matplotlib to determine if point belongs to the polygon. 
The following code:

>>> import numpy as np
>>> import matplotlib.nxutils as nx
>>> coords = np.array([[4.0, 1.0], [4.0, 4.0], [5.0, 5.0], [6.0, 4.0], [5.0, 0.0]])

>>> nx.pnpoly(4.0, 1.0, coords)
1
>>> nx.pnpoly(4.0, 4.0, coords)
1
>>> nx.pnpoly(5.0, 5.0, coords)
0
>>> nx.pnpoly(6.0, 4.0, coords)
0
>>> nx.pnpoly(5.0, 0.0, coords)
0

The question is why first two vertexes are considered to be inside of defined polygon, and last 3 vertexes are not? My guess, it's treating the polygon as a semi-open set, and I wonder if it can be changed to make all vertexes inclusive?

Any help would be greatly appreciated.

Many thanks,
Masha
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li...@us...