[R-sig-Geo] closest distance between irregularly-shaped polygons
Nick Matzke
matzke at berkeley.edu
Tue Feb 21 03:49:05 CET 2012
Hi everyone,
I have a number of irregularly-shaped polygons (from
shapefiles) in geographic (unprojected lat/long) coordinates.
I would like to measure:
1. the distance between the polygon centroids (which is
easy), and also
2. the *closest* distances of each polygon to each of the others
Is there an easy function or method for doing the latter?
If not, all I can think of is to cycle through all the
vertices and do point-to-point distances until I get the
closest, although this seems wasteful and might even give
the wrong answer in certain situations.
Any help or suggestions very much appreciated!
Thanks!
Nick
--
====================================================
Nicholas J. Matzke
Ph.D. Candidate, Graduate Student Researcher
Huelsenbeck Lab
Center for Theoretical Evolutionary Genomics
4151 VLSB (Valley Life Sciences Building)
Department of Integrative Biology
University of California, Berkeley
Graduate Student Instructor, IB200B
Principles of Phylogenetics: Ecology and Evolution
http://ib.berkeley.edu/courses/ib200b/
http://phylo.wikidot.com/
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Email: matzke at berkeley.edu
Mailing address:
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1005 Valley Life Sciences Building #3140
Berkeley, CA 94720-3140
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"[W]hen people thought the earth was flat, they were wrong.
When people thought the earth was spherical, they were
wrong. But if you think that thinking the earth is spherical
is just as wrong as thinking the earth is flat, then your
view is wronger than both of them put together."
Isaac Asimov (1989). "The Relativity of Wrong." The
Skeptical Inquirer, 14(1), 35-44. Fall 1989.
http://chem.tufts.edu/AnswersInScience/RelativityofWrong.htm
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