[R-sig-Geo] Note on variogram fitting with polynomial degree

[Caspar Hallmann]

Dear all,

I read in ASDAR: "Residual variograms are calculated by default when a
more complex model for the trend is used..."

However, I noticed that when using fit.variogram in gstat with an
additional option: degree=2, but keeping the formula as an intercept
only, does not account for the higher degree of complexity in the
model. I suspect this is not the intended behavior. To honour a
dependence structure (polyn degree) in my observations I need to state
the dependence explicitly in the formula.

Best regards,

Caspar

data(meuse)
coordinates(meuse) <- c("x", "y")
v<-variogram(log(zinc)~1,meuse)
print(v)
vs<-variogram(log(zinc)~1,meuse,degree=2)
print(vs)
vt<-variogram(log(zinc)~x*y+I(x^2)+I(y^2),meuse)
print(vt)

PS:
x86_64-w64-mingw32/x64 (64-bit)
R version 3.0.1 (2013-05-16)
gstat_1.0-16