[R] problem with nb2listw

[dagenais at ualberta.ca]

Hi,
I am a new student to R and I was hoping someone could help me with  
the error message I keep getting when I try to use the nb2listw()  
function.

I have 45 sites and I want to get an autocorrelation value for sites  
within 1000m of each other.

coords<-cbind(EAST,NORTH)
coords<-as.matrix(coords)
nb1000<-dnearneigh(coords,0,1000,longlat=TRUE)

then when I try to run the nb2listw(nb1000, style="W")
I get an error message of "Empty neighbour sets found". Can someone  
tell me what this means and how to possible fix it.

Thanks
Lynnette

~
Lynnette Dagenais
M.Sc. Candidate
Department of Renewable Resources
University of Alberta
Edmonton, AB