set of points form a polygon?

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kai
kai 2020-8-24
评论： kai 2020-8-24
Hello,
Is there a way to tell if a set of vertices can form a closed polygon or not in genear or in matlab ?
Example:
[1,1], [3,1],[2,2] form a triangle when connected.
How do you conclude that these points can form a polygon.
Is there any algorithm to follow ?.
Thank you.
  2 个评论
KSSV
KSSV 2020-8-24
Always more than two non-collinear points can form a polygon. If they are on striaght line/ collinear they cannot and this can be obtained by using area; you can use polyarea to get the area. If area is zero then they are collinear. If you have a value they can form polygon.
kai
kai 2020-8-24
Thank you KSSV for you answer
it helped me.

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采纳的回答

Bruno Luong
Bruno Luong 2020-8-24
编辑：Bruno Luong 2020-8-24
If your list of points are ordered of the boundary of the polygonal, you can detect if the list of points self intersect thus NOT represent a valid polygonal by using polyshape, catch the warning or get the number of regions, if it's larger than 1 it's not valid:
EDIT: you can also use ISSIMPLIFIED function
>> x=rand(1,5)
x =
0.1419 0.4218 0.9157 0.7922 0.9595
>> y=rand(1,5)
y =
0.6557 0.0357 0.8491 0.9340 0.6787
>> issimplified(polyshape(x,y,'Simplify',false))
ans =
logical
0 % <= NOT VALID
  1 个评论
kai
kai 2020-8-24
Thank you Bruno Luong for commenting the question and helping me.

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