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How can I test if a point is inside a certain polygon? How can I test if a lot of points are inside a certain polygon?

Answer 1

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Use the algorithm described on this site is decades old and well tested.

If you have matplotlib installed, you can use the implementation of this algorithm in matplotlib.nxutils, i.e.

from matplotlib.nxutils import pnpoly

This tests one. For testing an array of points use points_in_poly instead.

See also the matplotlib FAQ.

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updated2009-08-22 06:14:52
	dwf

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Answer 2

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At

http://mentat.za.net/source/pnpoly.tar.bz2

you'll find pure Python, ctypes and weave wrappers implementing this algorithm:

http://local.wasp.uwa.edu.au/~pbourke/geometry/insidepoly/

(same as in matplotlib, I believe)

Paul Bourke's website is an excellent reference for computational geometry!

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updated2009-08-22 12:35:44

asked 2009-08-22 12:34:23
	Stefan 31

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Answer 3

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The matplotlib way is probably the simplest. If you end up needing something fancier, check out the shapely package. If offers geometric classes such as Point and Polygon. Polygon has a contains method that checks whether or not another geometry is contained within its bounds.

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asked 2010-03-15 16:06:03
	Huard 1

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