chull() wanted?

Prof Brian D Ripley
Wed, 7 Apr 1999 15:46:44 +0100 (BST)

On Wed, 7 Apr 1999, Dipl.-Stat. Detlef Steuer wrote:

> Hello!
> Is there someone already working on an implementation of Splus'
> chull() function for R?
> If not, I would like volunteer to try it.
> For my "Diplom" I implemented convex peeling in C (some time ago),
>  using an O(n log(n)) algorithm, so it probably will prove relatively easy to
> use that code for a R-function.

If only you had volunteered a month ago!

There is one implementation in package sm, and a cleaner one in 0.64, due
out today.  Both as versions of Eddy's 1977 algorithm. I would be happy to
replace the present chull by something better, though. It doesn't do
peeling, but that is easy to arrange in R: just remove the convex hull and

Brian D. Ripley,        
Professor of Applied Statistics,
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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