Hi, The method I used to determine the infinite vertices is very close to David's approach. The main difference is to drop the border points that are equidistant to 2 or more input points.
- calculate the coordinates of all border points (all points just outside the minimum and maximum of input coordinates) - calculate the distance between all border points and input coordinates input and border are n by 2 matrices distance =: +/"1|input-"1"1 2 border - tag the input points that are a minimum distance to each border coordinate min=:(<./distance) ="1 distance - keep border points that correspond to only one input point min=: (1=+/min)#"1 min - list infinite vertices I. +./"1 min ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
