[R] Generating a polygon around points

[Tsjerk Wassenaar]

Hi Bob,

You probably want to have a look at the package alphahull.

Cheers,

Tsjerk


On Fri, Aug 15, 2014 at 5:25 PM, Clint Bowman <clint at ecy.wa.gov> wrote:

> Your question seems to need an answer to, "How do you find a convex hull
> on a sphere?"  Google has many references.
>
> Clint Bowman                    INTERNET:       clint at ecy.wa.gov
> Air Quality Modeler             INTERNET:       clint at math.utah.edu
> Department of Ecology           VOICE:          (360) 407-6815
> PO Box 47600                    FAX:            (360) 407-7534
> Olympia, WA 98504-7600
>
>         USPS:           PO Box 47600, Olympia, WA 98504-7600
>         Parcels:        300 Desmond Drive, Lacey, WA 98503-1274
>
>
> On Fri, 15 Aug 2014, Bob O'Hara wrote:
>
>  I've been struggling for half a day on what should be a simple problem...
>>
>> I have a data frame of lat/long coordinates that describe a region, and I
>> want to draw a polygon around them so I can use that as a boundary (to be
>> thrown at INLA, but those details aren't important). The coordinates are
>> almost on a regular grid: there is some variation in latitude (because
>> we're on a globe).
>>
>> If the coordinates were on a regular grid, I could use as.owin() to create
>> a mask, and go on from there (I have code that will work). But as.owin()
>> doesn't like unevenly spaced points.
>>
>> Can anyone suggest a way to sort this out? Preferable without having to
>> mess around transforming the coordinates.
>>
>> Bob
>>
>> --
>> Bob O'Hara
>>
>> Biodiversity and Climate Research Centre
>> Senckenberganlage 25
>> D-60325 Frankfurt am Main,
>> Germany
>>
>> Tel: +49 69 798 40226
>> Mobile: +49 1515 888 5440
>> WWW:   http://www.bik-f.de/root/index.php?page_id=219
>> Blog: http://occamstypewriter.org/boboh/
>> Journal of Negative Results - EEB: www.jnr-eeb.org
>>
>>         [[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.
>



-- 
Tsjerk A. Wassenaar, Ph.D.

	[[alternative HTML version deleted]]