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]]

