[Openspace] nb2listw

[mohamed ben ahmed]

 Dear  Members,
Can anyone tell me how to resolve this problem:
for spatial data and using R, i created the contiguité list:
staterook<-read.gal("rook.GAL"), it's ok
but when i wanted to create the weight list by;
staterook1<-nb2listw(statetook) , a message of error appears and say:
Erreur dans nb2listw(staterook) : Empty neighbour sets found
thnak you in advance
Best Regards