h_Section 11 (variogram)

# install.packages( c("gstat", "sf", "spData" ) )
library(gstat)
library(sf)
library(spData)

##### Meuse data
data(meuse)
meuse[1:5,]
meuse_sf <-st_as_sf(meuse, coords = c("x", "y"), crs = 28992)
plot(meuse_sf[,"zinc"], pch=20, axes=TRUE)

##### variogram cloud
formula  <-log(zinc) ~ soil + ffreq + dist
cvario   <-variogram(formula,data=meuse_sf,cloud=TRUE)
plot(cvario)

##### empirical variogram
vario   <-variogram(formula,data=meuse_sf)
plot(vario)

vario   <-variogram(formula,data=meuse_sf,cut=1300, width=50)
plot(vario)

##### variogram model
varioSph<-fit.variogram(vario, vgm(psill=0.015, "Sph", range=700, nugget=0.05))
varioExp<-fit.variogram(vario, vgm(psill=0.015, "Exp", range=700, nugget=0.05))
varioGau<-fit.variogram(vario, vgm(psill=0.015, "Gau", range=700, nugget=0.05))

plot(vario,varioSph)
plot(vario,varioExp)
plot(vario,varioGau)

varioSph
varioExp
varioGau

attr(varioSph, "SSErr")
attr(varioExp, "SSErr")
attr(varioGau, "SSErr")