Please excuse these basic questions, but I am a bit lost in geostatistics.
I am trying to make a kriging of the soil properties of a plot. I am
already using gstat with R and I don't have any problems with the scripts
and so on...but, I don't really know how to choose the nugget, psill and
range for the variogram model. Moreover, I am not sure about how to include
the anisotropy in the model, I have already include a linar model in some
cases, to remove any trend.
I am following the steps recomended in the gstat help, but I am a bit
befuddled.
Let me show you my scripts (the psill, range and nugget are choosen just to
make the test).
coordinates(corg)= c("x", "y")
v = variogram(SOC~1, corg)
SSErr.a <- numeric(4)
names(SSErr.a) <- c("Exponencial","Esférico","
Gausiano","Lineal")
v.fit = fit.variogram(v, vgm(psill=0.18, model="Exp", range=5, nugget=0.1))
SSErr.a[1] = attr(v.fit, "SSErr")
v.fit = fit.variogram(v, vgm(psill=0.18, model="Sph", range=5, nugget=0.1))
SSErr.a[2] = attr(v.fit, "SSErr")
v.fit = fit.variogram(v, vgm(psill=0.18, model="Gau", range=5, nugget=0.1))
SSErr.a[3] = attr(v.fit, "SSErr")
v.fit = fit.variogram(v, vgm(psill=0.18, model="Lin", range=5, nugget=0.1))
SSErr.a[4] = attr(v.fit, "SSErr")
SSErr.a
v = variogram(SOC~x+y, corg)
SSErr.b <- numeric(4)
names(SSErr.b) <- c("Exponencial","Esférico","Gausiano","Lineal")
v.fit = fit.variogram(v, vgm(psill=0.18, model="Exp", range=5, nugget=0.1))
SSErr.b[1] = attr(v.fit, "SSErr")
v.fit = fit.variogram(v, vgm(psill=0.18, model="Sph", range=5, nugget=0.1))
SSErr.b[2] = attr(v.fit, "SSErr")
v.fit = fit.variogram(v, vgm(psill=0.18, model="Gau", range=5, nugget=0.1))
SSErr.b[3] = attr(v.fit, "SSErr")
v.fit = fit.variogram(v, vgm(psill=0.18, model="Lin", range=5, nugget=0.1))
SSErr.b[4] = attr(v.fit, "SSErr")
SSErr.b
Thanks a lot,
Cheers.
--
Julia Chacon Labella [PhD candidate]
Área de Biodiversidad y Conservación
Escuela Superior de Ciencias Experimentales y Tecnología
Universidad Rey Juan Carlos
c/ Tulipán, s/n.
E-28933 Móstoles (Madrid)
España
--
Julia
[[alternative HTML version deleted]]
_______________________________________________
R-sig-Geo mailing list
R-sig-Geo@r-project.org
https://stat.ethz.ch/mailman/listinfo/r-sig-geo
