Dear there
I am trying to construct spatial weight matrix using inverse distance, which
means that high weight is given to near observations and ,vies versa, where
w_ij=w_ji and w_ii=0, Since, I am a new R user, I've tried many functions in
sp,spdep packages and I find some functions to find weight matrix by using
nearest neighbours and by distance-based neighbours, but I want to use all
observations as neighbours and based on the inverse distance, I can construct
the weights.
Before I write the code I'll give some information about my data, I have the
coordinates of 51 states (US states) , thus latitude and longitude of each
states and based on the distance between each state I will give a weight for
states where the weight is the the inverse of the distance. obviously , the
weight matrix are symmetric.
Then I've tried the following code
data(location)# data.frame with 2 col and 51 row
loc.sp = SpatialPoints(cbind(location$latitude,location$longitude))
sy8<-knn2nb(knearneigh(loc.sp,k=50)) # for each state all other states are
considered as neighbour
dsts<-nbdists(sy8, loc.sp)
idw<-lapply(dsts, function(x) 1/(x))
sy<-nb2listw(sy8, glist=idw, style="B")
col.mat <- listw2mat(sy)
after running this code, I got symmetric matrix (51* 51), where w_ii=0 and
w_ij=w_ji
but I am not sure if this is true!!!
any commands and helps are appreciated
Regards,
Alsulami
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