I am modeling a trend surface using trmat and want to trim the resulting matrix to the area enclosed by my real data (i.e., remove all the extrapolated areas).  I was using chull and in.chull to calculate the convex hull and change all the other values created by trmat to NA.  However, my real data has portions that are slightly concave so chull would give me slivers that are extrapolations from my data.  Is there some other type of "chull" function that will allow the resulting polygon to be slightly concave?  (I can send a picture to show what I am trying to do, if needed)

Thanks in advance,
Mike

Mike R. Saunders
Forest Biometrician
Cooperative Forest Research Unit
University of Maine
5755 Nutting Hall
Orono, ME  04469-5755

207-581-2763 (O)
207-581-2833 (F)

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