[R-sig-Geo] closest distance between irregularly-shaped polygons

[Kemp, Michael]

Hey Nick,

There was a previous discussion on this topic in the R-sig-geo mailing list.  Follow the discussion here...
https://stat.ethz.ch/pipermail/r-sig-geo/2009-March/005216.html

Hope this helps.
Regards,
Michael


-----Original Message-----
From: r-sig-geo-bounces at r-project.org [mailto:r-sig-geo-bounces at r-project.org] On Behalf Of Nick Matzke
Sent: Tuesday, February 21, 2012 3:49 AM
To: r-sig-geo at r-project.org
Subject: [R-sig-Geo] closest distance between irregularly-shaped polygons

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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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.
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