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I am using vgm() from the gstat library in R:

variogr <-vgm(sill,"Exp",range=range,nugget=0)
output <-krige(...,model=variogr)

As you can see I'm using fixed psill and range values.

Before this, another script (on which I have not control) is evaluating the variogram parameters. Namely, I know that my points fit well in a p1*(1-exp(-x/p2)), and I am given the exact values of p1 and p2. My question is how to get sill and range (sill and range) from the exponential model parameters p1 and p2?

I know that the sill value is == p1, because we are choosing nugget to be zero. But I'm having troubles finding which value should I give to the range. I have been told by my professor that range == p2, but from what I have read elsewhere there should also be a factor (like, p2 == k*range) that might have different values depending on the proper definition of range.

So, given p1 and p2, which value should I use as a range input to the vgm() function? Is it true that range == p2? What kind of range is vgm() expecting me to put in?

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Yes, this is true. Your professor is right. Look for function fn_exponential in the source code if you want to be sure.

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