[R] Distances between two datasets of x and y co-ordinates

From: <adrian_at_maths.uwa.edu.au>
Date: Fri, 14 Mar 2008 12:52:42 +0900 (WST)


Andrew McFadden <Andrew.McFadden_at_maf.govt.nz> writes:

> I am trying to determine the distances between two datasets of x and y
> points.

This can be done efficiently in the package 'spatstat'.

     library(spatstat)
     crossdist(x1, y1, x2, y2)

where x1, y1 are vectors of coordinates for the first set of points and x2, y2 for the second set. See help(crossdist.default)

This is executed in C and is faster than using outer() or apply().

The result is a matrix giving the distance between each pair of points (the first point in the first dataset and the second point in the second set). If these datasets are large, you can of course run into trouble with the size of this matrix.

If you just wanted to find the distance to the *nearest* point (or identify which point is nearest), use the function nncross().

Adrian Baddeley



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