[R-sig-Geo] Voronoi polygons using tripack package....
Roger.Bivand at nhh.no
Mon Apr 25 19:34:44 CEST 2005
On Mon, 25 Apr 2005 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.
If you look at the code in tri2nb() in the spdep package, you may see an
easy way to get what you need, even if the nb object is overkill. In fact,
neighbours(tri.mesh(x, y)), using functions from tripack, should be
enough, returning a list with the point numbers.
> 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
> > for large point datasets. So far the program appears to work well,
> > 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
> > 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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e-mail: Roger.Bivand at nhh.no
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