[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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-----------------------------------------------------
"[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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