# nndist R vs. ArcGIS

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## nndist R vs. ArcGIS

 Can anyone tell me why I would get different average nearest neighbor values for the same set of coordinates between ArcGIS 10 and R? Sometimes the difference in distance is over 1.3 km. Alexis
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## Re: nndist R vs. ArcGIS

 Alexis wrote: > Can anyone tell me why I would get different average nearest neighbor values > for the same set of coordinates between ArcGIS 10 and R? Sometimes the > difference in distance is over 1.3 km. spatstat::nndist calculates Euclidean distances rather than distances along the earth's surface, which is probably what you're getting from AG. A very short example illustrating the problem would be helpful in determining if I'm at all right; on the other hand I'm glad you're testing your results. You might peek at the current thread "Geographic distance between lat-long points in R" for more information. cur -- Curt Seeliger, Data Ranger Raytheon Information Services - Contractor to ORD [hidden email] 541/754-4638         [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: nndist R vs. ArcGIS

 In reply to this post by smoluka On Mon, Apr 11, 2011 at 4:49 PM, smoluka <[hidden email]> wrote: > Can anyone tell me why I would get different average nearest neighbor values > for the same set of coordinates between ArcGIS 10 and R? Sometimes the > difference in distance is over 1.3 km.  Edge correction? In a spatial point pattern, points near the boundary of your window are less likely to have a near neighbour because only some of the surrounding space can possibly have points. I think functions in spatstat will correct for this. Make a simple test example and tell us what functions you are using. And also try the r-sig-geo mailing list  for this sort of thing. Barry ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.