[R-sig-Geo] create nb object
pslarson2 at gmail.com
Thu Dec 17 13:38:15 CET 2009
OK, I did what you indicated here:
with a summary:
Neighbour list object:
Number of regions: 341
Number of nonzero links: 341
Percentage nonzero weights: 0.2932551
Average number of links: 1
Non-symmetric neighbours list
Then I want to run a spatial regression like this:
spautolm(N.fish.spp ~ TEMPannual + Elevation, data=fish,
and I get this error:
Error in spautolm(N.fish.spp ~ TEMPannual + Elevation, data = fish,
family = "SAR", :
No neighbourhood list
I thought that the "test" object WAS a neighborhood list?
Any help would be appreciated.
Roger Bivand wrote:
> On Wed, 16 Dec 2009, Pete Larson wrote:
>> Hello all,
>> I have a data frame with lat and lon coordinates for some sample
>> areas (not a grid) .
>> I was to create an nb object that I can use with spdep but am unsure
>> as to how to convert it.
>> Does anybody have any ideas?
> Create a matrix of coordinates, if not using sp classes, for example:
> xy <- cbind(df$x, df$y)
> or if your data frame is a SpatialPointsDataFrame, just:
> xy <- coordinates(obj)
> Then your choice of dnearneigh(), knn2nb(knearneigh()), graph2nb()
> with three graph variants, tri2nb() for a Delaunay triangulation. The
> first two of these also take a longlat= argument in case your
> coordinates are geographical, not projected. Triangulation and
> graph-based methods need planar coordinates, so you would have to
> project them first.
> Hope this helps,
>> R-sig-Geo mailing list
>> R-sig-Geo at stat.math.ethz.ch
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