[R] Concave Hull

[David Winsemius]

The OP was asking whether concave hulls have been implemented. He  
wasn't very helpful with his link giving the example, since it was to  
the "outside" of a frame-based website. Perhaps this link (see the  
bottom of that page) will be more helpful:

http://get.dsi.uminho.pt/local/results.html

It has been discussed (briefly) in r-help:
http://finzi.psych.upenn.edu/R/Rhelp02a/archive/75574.html

Some of the material in Loader's "Local Regression and Likelihood"  
regarding classification looks potentially applicable.

When first I saw this question I expected that one of the r-sig-Geo  
folks would have a ready answer. Perhaps a follow-up there would be a  
reasonable next step?

-- 
David Winsemius

On Jan 20, 2009, at 6:37 PM, Charles Geyer wrote:

>> Message: 64
>> Date: Mon, 19 Jan 2009 15:14:34 -0700
>> From: Greg Snow <Greg.Snow at imail.org>
>> Subject: Re: [R] Concave Hull
>> To: Michael Kubovy <kubovy at virginia.edu>, r-help
>> 	<r-help at r-project.org>
>> Message-ID:
>> 	<B37C0A15B8FB3C468B5BC7EBC7DA14CC61C8360835 at LP-EXMBVS10.CO.IHC.COM>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> I don't know if it is the same algorithm or not, but there is the  
>> function "chull" that finds the convex hull.
>
> Also the R function "redundant" in the contributed package "rcdd"  
> efficiently
> finds convex hulls in d-dimensional space for arbitrary d (chull  
> only does
> d = 2).  See Sections 4.2 and 5.2 of the rcdd package vignette.
>
>> Hope this helps,
>>
>> -- 
>> Gregory (Greg) L. Snow Ph.D.
>> Statistical Data Center
>> Intermountain Healthcare
>> greg.snow at imail.org
>> 801.408.8111
>>
>>
>>> -----Original Message-----
>>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
>>> project.org] On Behalf Of Michael Kubovy
>>> Sent: Saturday, January 17, 2009 9:49 AM
>>> To: r-help
>>> Subject: [R] Concave Hull
>>>
>>> Dear Friends,
>>>
>>> Here is an algorithm for finding concave hulls:
>>> http://get.dsi.uminho.pt/local/
>>>
>>> Has anyone implemented such an algorithm in R?
>>>
>>> RSiteSearch('concave hull') didn't reveal one (I think).
>>>
>>> _____________________________
>>> Professor Michael Kubovy
>>> University of Virginia
>>> Department of Psychology
>>> Postal Address:
>>> 	P.O.Box 400400, Charlottesville, VA 22904-4400
>>> Express Parcels Address:
>>> 	Gilmer Hall, Room 102, McCormick Road, Charlottesville, VA 22903
>>> Office:    B011;		Phone: +1-434-982-4729
>>> Lab:        B019;		Phone: +1-434-982-4751
>>> WWW:    http://www.people.virginia.edu/~mk9y/
>>> Skype name: polyurinsane
>>>
>>>
>>>
>>>
>>>
>>> 	[[alternative HTML version deleted]]
>>>
>>> ______________________________________________
>>> R-help at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-help
>>> PLEASE do read the posting guide http://www.R-project.org/posting-
>>> guide.html
>>> and provide commented, minimal, self-contained, reproducible code.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.