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I have 54 points in one data set A I have 300+ data points in a dataset B.

I wish to find the distance for each point in dataset-set B, to points in dataset A.

Nearest Neighbor packages appear to only find neighbors within a given data-set, not a second data set.

rdist was close, but I didn't want a matrix, just nearest.--"Given two sets of locations computes the full Euclidean distance matrix among all pairings or a sparse version for points within a fixed threshhold distance."

This looked good, saying "Read two geocoded point sets from Comma Separated Value (CSV) files into R data objects. Assign to each member of first point set the geographically closest point from second set" but is so dated (2010), so something more recent must exist...

Same issue with this

Other packages find distances between points and lines, points and polygons, etc. viz: http://cran.r-project.org/web/packages/geosphere/geosphere.pdf

The omission of P2P suggests I am missing something simple...

  • What nearest neighbour packages? kdtree in nabor is likely to be the most efficient, but if you need ellipsoid distances you can roll your own with spDistsN1 in sp. – mdsumner Dec 20 '14 at 1:00
  • Have you considered using GRASS GIS for the distance analysis? I'm sure googling would come up with the correct "v." command, then invoke R fromwithin GRASS? – Spatial Digger May 11 '16 at 6:45
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UPDATE:

The FNN package has a function get.knnx which can compute the N-nearest neighbours in point patterns. For what you want, this should work:

nn = get.knnx(A,B,k=1)

Which should just return the nearest neighbors between the two datasets. You can also specify what nearest neighbor algorithm it will use, be it kd_tree, cover_tree, CR, or brute force.


spatstat has a crossdist function.

Description

Computes the distances between pairs of ‘things’ taken from two different datasets.

It takes two point patterns A and B as inputs, and returns the matrix whose [i,j] entry is the distance from A[i] to B[j]. To get the nearest neighbors between two datasets using crossdist:

xdistances <- crossdist(A, B)  #Get all cross distances    

nn = numeric() 
for (i in 1:nrow(A)) {   
  xdistance <- sort(xdistances[i,], partial=1)[1]   
  nn <- append(nn, xdistance)
}

I hope that helps.

  • This does solve the problem I've articulated. But I'm also hoping to use the function on a much larger table, where set B contains 5K pts, or 50K points, or 500K points. It just seems like there should exist an R package that doesn't waste computation so, that would just find the distance to the nearest point, rather than all points. – Mox Dec 22 '14 at 5:49
  • Updated my answer. I hope it works. – R.K. Dec 22 '14 at 6:14
  • Thank you. I am much obliged. Your solution does seem to be the general one--I see it and similar solutions cropping up over and over, like so: stackoverflow.com/questions/22121742/… – Mox Dec 22 '14 at 6:17
  • If you found it useful, do upvote it. It sends the message that it did answer your question to some extent and it'll give me the peace of mind that I didn't just waste a fraction of my life trying to solve problems for random strangers on the internet. ;-) – R.K. Dec 22 '14 at 6:31
  • Happily. My apologies for not doing so sooner. – Mox Dec 22 '14 at 6:35
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RANN looked like the package I was looking for, but was not... RANN gives the nearest neighbor for CELLS, not an XY point layer.

FNN was the package I was looking for.

Alternates methods exist, but share commonalities: All methods make use of a) A distance function b) loop or apply c) A 'min' of the distance function

Examples:

https://stackoverflow.com/questions/22121742/calculate-the-distance-between-two-points-of-two-datasets-nearest-neighbor

https://stackoverflow.com/questions/21977720/r-finding-closest-neighboring-point-and-number-of-neighbors-within-a-given-rad

  • Could you give some examples of how you made it work? – Simbamangu Dec 21 '14 at 17:47

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