> I have a bunch of geographic locations specified by lat-long > coordinates. What's an easy way to calculate geographic distance > between any two points? OR, perhaps there is a function for > calculating a distance matrix for K sites?
A comparison of some geographic distance calculations is provided at http://pineda-krch.com/2010/11/23/great-circle-distance-calculations-in-r/ , along with code for calculating the Vincenty inverse formula, which relies on the WGS-84 ellipsoid approximations. The author compares the results to fields::rdist.earth, which seems to rely on a spherical model of the earth. It would be interesting to compare it to other distance functions as well. I found that the function provided at the above URL did not handle the case of coincident points. Adding the following line after the while loop fixed this. if (iterLimit==100) return(0) # formula began with nearly or exactly coincident points Enjoy the days, cur -- Curt Seeliger, Data Ranger Raytheon Information Services - Contractor to ORD seeliger.c...@epa.gov 541/754-4638 [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
