set of points form a polygon?

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.

[KSSV]

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]

Thank you KSSV for you answer

it helped me.

Answer 1

[Bruno Luong]

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

[kai]

Thank you Bruno Luong for commenting the question and helping me.