[R-sig-Geo] Voronoi polygons: New question: Spatial Registration of spatial data layers?
Rick Reeves
reeves at nceas.ucsb.edu
Thu Apr 28 02:58:38 CEST 2005
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]]
> > >
> > > _______________________________________________
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> > > R-sig-Geo at stat.math.ethz.ch
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> >
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> --
> Tim Keitt
> Section of Integrative Biology
> http://www.keittlab.org/
>
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