Thanks for everyone's advice and suggestions on this topic;

Looks like the cells() method of tripack provides me with

the information I need to solve my problem.

Now, if you don't mind, another question. Is it possible to

spatially register multiple data layers (in the classic GIS

fashion) so as to identify multiple attributes from all the

layers for the same geographic coordinate? The 'point in

polygon' problem, with multiple map layers.

No doubt I could (and would) solve this using GRASS and the

R interface, but several ecologists here at the Center

would like to have an 'R only' solution.

Thanks for any information, links, .pdfs, etc..

Rick Reeves

Scientific Programmer / Quantitative Analyst

National Center for Ecological Analysis and Synthesis

University of California, Santa Barbara

805 892 2534

reeves at nceas.ucsb.edu

-----Original Message-----

From: r-sig-geo-bounces at stat.math.ethz.ch

[mailto:r-sig-geo-bounces at stat.math.ethz.ch] On Behalf Of

White.Denis at epamail.epa.gov

Sent: Monday, April 25, 2005 11:54 AM

To:

Subject: Fw: [R-sig-Geo] Voronoi polygons using tripack package....

Assuming the same triangulation algorithm is used in tri.mesh as in

voronoi.mosaic (likely if in the same package, haven't looked at the

details). But see

http://www.cse.unsw.edu.au/~lambert/java/3d/delaunay.html for

alternatives.

r-sig-geo-bounces at stat.math.ethz.ch wrote on 2005-04-25 11:26:34:

> On Mon, 2005-04-25 at 10:18 -0700, White.Denis at epamail.epa.gov wrote:

> > Tripack also calculates the Delauney triangulation (tri.mesh) which

is

> > the dual of the Voronoi tessellation. I haven't looked at the data

> > structure, but the first order neighbors in the triangulation are

also

> > the Voronoi neighbors I believe.

>

> Yes, that has to be true by definition as the Varonoi arcs bisect the

> Delauney arcs.

>

> THK

>

> >

> > r-sig-geo-bounces at stat.math.ethz.ch wrote on 2005-04-25 09:57:13:

> >

> > >

> > >

> > > Greetings:

> > >

> > > We are beginning to use the tripack package to generate voronoi

> > polygons

> > >

> > > for large point datasets. So far the program appears to work well,

> > even

> > > for

> > > datasets in the 100,000 size class.

> > >

> > > One thing we need to do is to identify all of the neighbor

polygons of

> > > each

> > > polygon. Neighbor criteria is: two polygons are neighbors if they

> > share

> > > at

> > > least one edge (line segment).

> > >

> > > The 'cells' and 'methods' method on the voronoi object porport to

find

> > > the neighbors

> > > of veronoi cells. But these operate on the voronoi object, not the

> > > voronoi polygon

> > > object.

> > >

> > > I am wondering if anyone has used or extended the tripack.voronoi

> > > methods to

> > > calculate voronoi polygons and their neighbors, or found a more

> > > suitbable R

> > > package to do so.

> > >

> > >

> > > Thanks in advance,

> > >

> > > Rick Reeves

> > > Scientific Programmer

> > > National Center for Ecological Analysis and Synthesis

> > > UC Santa Barbara

> > >

> > > [[alternative HTML version deleted]]

> > >

> > > _______________________________________________

> > > R-sig-Geo mailing list

> > > R-sig-Geo at stat.math.ethz.ch

> > >

https://stat.ethz.ch/mailman/listinfo/r-sig-geo> >

> > _______________________________________________

> > R-sig-Geo mailing list

> > R-sig-Geo at stat.math.ethz.ch

> >

https://stat.ethz.ch/mailman/listinfo/r-sig-geo> --

> Tim Keitt

> Section of Integrative Biology

>

http://www.keittlab.org/>

> _______________________________________________

> R-sig-Geo mailing list

> R-sig-Geo at stat.math.ethz.ch

>

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