How to find the the boundary co-ordinates from a given set of co-ordiantes?

I understand that this question asked previously and answered here

Finding boundary co-ordinates from given set of point co-ordinates?

But the answers given here are about the estimates of the the convex hull of the set.

How could we get the boundary points only?

  • If you can, upload a figure of what you are asking. You might need to put a link to it in the comments as you don't have enough "points" to do this, but someone else can help you with that. – Mike T Nov 2 '14 at 20:19
  • Create the convex hull, calculate the point distance from each point in the set to the closest vertex on the hull and select any with distance equal to 0... depending on your software you may be able to 'select by location' from the points using the convex hull boundary. A few more specifics might help refine the instructions. – Michael Stimson Nov 3 '14 at 0:54
  • The thread you reference provides many ways to obtain vertices of the convex hull. What distinction are you making, then, in asking for them "explicitly"? – whuber Nov 3 '14 at 18:16
  • I just want the boundary points. I edited it. – Janak Nov 4 '14 at 17:58
  • Methods to extract vertices from polygons are numerous, depending on the software: search our site. Algorithms--which your tags seem to be requesting--return the vertices explicitly, in order, around the convex hull, and are provided in answers to the question you reference. – whuber Nov 4 '14 at 18:51