Dear all, please, I am looking to understand how the two functions ("inpolygon ()" and "boundary()") work ?

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Ammar 2017-1-11

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评论： KSSV 2017-1-12

Dear all, Please, I have a question: I know the function "inpolygon()" give me a logical result if a data point inside or outside a polygon and "boundary()" give me the data points on the border of a shape. But how these two algorithms work ?

Please, I need to understand them.

Kind regards Ammar

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Answer 1

KSSV 2017-1-11

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https://ww2.mathworks.cn/matlabcentral/answers/319953-dear-all-please-i-am-looking-to-understand-how-the-two-functions-inpolygon-and-boundary#answer_250184

From a given point P, the code draws a straight onto the given polygon. If this line intersects even number of times then the point lies outside the polygon, if the line intersects odd number points then points lies inside the polygon. The code is based on the refer article:

http://ac.els-cdn.com/S0925772101000128/1-s2.0-S0925772101000128-main.pdf?_tid=369ef44e-d7eb-11e6-b220-00000aab0f01&acdnat=1484131771_c505af2dfb8307ef1d0f8eef55733999

For outline refer:

https://en.wikipedia.org/wiki/Point_in_polygon