Characterizing the position (central vs > peripheral) of a point in a point pattern - R-SIG-Geo

Thu, Apr 30, 2009 1:28 PM #

Hi Alex
I think the following might be close to what you want;
1) calculate the convex hull of your point set
2) Calculate the centroid of the convex hull polygon
3) for each point:
   calculate the distance to the centroid (d_c)
   calculate the distance to the closest boundary (d_b)
4) interior = d_c < d_b

If this simple 50/50 rule is to simple, you could use convex hull
peeling
to determine the exterior points for some threshold, eg the outer 30% of
the data.

hope this helps
Nicholas