makeneighborsw {GeoXp} | R Documentation |
The function `makeneighborsw' create a spatial weight matrix based on a given number of nearest neighbors (option "neighbor" by default), based on a threshold distance (option method="distance") or both these 2 methods.
makeneighborsw(xc,yc,method="neighbor",m=1,d,cum=TRUE)
xc |
a vector $x$ of size $n$ |
yc |
a vector $y$ of size $n$ |
method |
"neighbor" by default, "distance" or "both" |
m |
number of nearest neighbors |
d |
threshold point |
cum |
if cum=TRUE, $W$ is the sum of spatial weight matrix based on $k$ nearest neighbours (for $k <=q m$; if FALSE $W$ is the spatial weight matrix based only on $m^{th}$ nearest neighbours |
In the case of method="neighbor", for each site, we order the other sites by their distance from this site. If cum=TRUE, for $i$, if $j$ is among the $m^{th}$ nearest sites, then :
W_{ij}=1
else
W_{ij}=0
If cum=FALSE, for $s_i$, if $s_j$ is the $m^{th}$ nearest site, then :
W_{ij}=1
else
W_{ij}=0
In case of ties, the nearest neighbour is randomly chosen.
In the case of method="distance", if site $i$ is seperated from $j$ by a distance lower
or equal to a given threshold :
W_{ij}=1
else
W_{ij}=0
In the case of method="both" W must verify the two first conditions.
A spatial weight matrix of size $n times n$
Aragon Y., Thomas-Agnan C., Ruiz-Gazen A., Laurent T., Robidou L.
Aragon Yves, Perrin Olivier, Ruiz-Gazen Anne, Thomas-Agnan Christine (2008), ``Statistique et Econométrie pour données géoréférencées : modèles et études de cas''
# data auckland data(auckland) x.ext <- auckland$Easting[1:10] y.ext <- auckland$Northing[1:10] #plot(x.ext,y.ext,type='p') #text(x.ext,y.ext,as.character(1:10)) # matrix based on 5 nearest neighbors W<-makeneighborsw(x.ext,y.ext,method="neighbor",m=3) # matrix based on a threshold distance W1<-makeneighborsw(x.ext,y.ext,method="distance",d=20) # matrix based on the two methods W2<-makeneighborsw(x.ext,y.ext,method="both",m=3,d=20)