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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