Function for computing a matrix of gaussian or fixed weights from distance matrix
Usage
spweights(distmat, h = NULL, kernel = "gaussian")
Arguments
distmat
a symmetric matrix of inter-site distances (in km).
h
parameter of the Gaussian distance decay function.
kernel
indicates the type of weighting function, either 'fixed' or 'gaussian'. Default is 'gaussian'.
Value
An object of class spatialweights
Details
This function generates a weight matrix (required for the SPpermTest) function. When kernel=="fixed", the weight \(w_{ij}\) between site \(i\) and \(j\) is equal to 1 when their interdistance \(d_{ij}\) is below h, and equal to 0 when \(d_{ij}>h\).When kernel=="gaussian", the weight is calculated with formula exp(-d_ij^2/h^2).
# NOT RUN {lon <- c(11.3426,0.1278,0.1218)
lat <- c(44.4949,51.5074,52.2053)
library(sp)
d <- spDists(x=cbind(lon,lat),y=cbind(lon,lat))
spweights(d,h=100)
spweights(d,h=100,kernel="fixed")
# }