Hello All!
I calculate a variogram using the function variog (package geoR)
afterwards I use variofit to fit a spherical model (see code below).
Now I just changed the units of the variable (in this case MPa to kPa
just a factor of 1000). If I do so, I get a different fit and
therefore different ranges etc. Why? The semi-variance is of course 6
orders of magnitude higher but the values are the same. So from my
point of view it should be the same fit. Maybe there is a reason for
this I do not get.
Hopefully someone could reply to this question.
Thanks, Sascha Bellaire!
Parts of code, just multiplying wl1$PSI with 1000 changed it.
#Calculate the extent of the current "sampling" design
locations <- cbind(wl1$X,wl1$Y)
extent <- max(dist(locations))
max.dist <- extent/2
data1 <- cbind(wl1$X,wl1$Y,wl1$PSI*1000)
geodata1 <- as.geodata(data1, coords.col = 1:2, data.col = 3)
# Calculate the sample variogram
vario_var1 <- variog(geodata1,
uvec = nlags,
trend = trend,
option = "bin",
estimator.type = "modulus",
max.dist = max.dist,
pairs.min = 10.,
direction = "omnidirectional",
messages = TRUE)
# Fit a model
variofit_var1 <- variofit(vario_var1,
cov.model = variotype,
fix.nugget = FALSE,
max.dist = vario_var1$max.dist,
messages = TRUE)
___________________________________
Sascha Bellaire
WSL Institute for Snow and Avalanche Research SLF
Formation of Alpine Natural Hazards
Flüelastrasse 11
7260 Davos Dorf, Switzerland
Tel.: +41 81 4170 292
Fax: +41 81 4170 110
www.slf.ch
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