Voronoi polygons: New question: Spatial Registration of spatial data layers?
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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