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 -- View this message in context: http://r.789695.n4.nabble.com/nndist-R-vs-ArcGIS-tp3442375p3442375.html Sent from the R help mailing list archive at Nabble.com.
nndist R vs. ArcGIS
5 messages · smoluka, Seeliger.Curt at epamail.epa.gov, Barry Rowlingson +1 more
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On Mon, Apr 11, 2011 at 4:49 PM, smoluka <smoluka at geo.oregonstate.edu> 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
On 12/04/11 07:32, Barry Rowlingson wrote:
On Mon, Apr 11, 2011 at 4:49 PM, smoluka<smoluka at geo.oregonstate.edu> 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.
No. Not as far as I am aware or can discern. The function
nndist() does ***not*** invoke any edge correction. It simply
calculates the distances as they are, for the points that appear
in the window, and takes the appropriate minima.
cheers,
Rolf Turner
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
The problem was on the ArcGIS 10 end. The program corrupted my layers. I re-created the layer and now I get the same answer. Thank you all for your insight. Alexis PS, the scale is in terms of owl territories and therefore 1.3 km is really huge. -- View this message in context: http://r.789695.n4.nabble.com/nndist-R-vs-ArcGIS-tp3442375p3444701.html Sent from the R help mailing list archive at Nabble.com.