Hi there,
  Take the data of columbus(spdep) as an example. Say “i” is one of the
polygons, and “j” represents its neighbours. How to get the vlues of
“sum(Wij*Xj)”?  “Wij” means the weights, which can be get by
“nb2listw$weights”.
Say “Xj” to be “columbus$PLUMB”. The problem is how to get the right values
of “columbus$PLUMB” for the corresponding neighbours, so i can calculate the
"sum(Wij*Xj)"? See the following example.
example(columbus);coords <- coordinates(columbus)
nbs <- dnearneigh(coords,0,4)
nbslistw<-nb2listw(nbs, style="B")
#nbslistw$neighbours; nbslistw$weights
 I can not figure it out. Anybody can give me some suggestions?
Thanks.

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Jane Chang
Queen's

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