[R] Concave Hull

[roger koenker]

Actually,  I think that the survey on "alpha shapes" available from:

	http://www.cs.duke.edu/~edels/Surveys/

would be more closely aligned with what Michael was interested in...


url:    www.econ.uiuc.edu/~roger                Roger Koenker
email   rkoenker at uiuc.edu                       Department of Economics
vox:    217-333-4558                            University of Illinois
fax:    217-244-6678                            Champaign, IL 61820


On Jan 20, 2009, at 6:06 PM, David Winsemius wrote:

> 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.
>
> ______________________________________________
> 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.