R version 3.3.2, Windows 10: gstat package: Error in fitting a variogram model using 'fit.variogram' function

Dear Members,



I am trying to fit a variogram model using fit.variogram function from the gstat package. The figure showing my experimental variogram can be seen here: https://i.stack.imgur.com/UZXw4.png

My code line for this operation is:

c2.vgm.fit<-fit.variogram(c2.vgm.exp,vgm(nugget=0, psill=400,model="Exp",range =40000),fit.method = 7)

The system throws following error message:

Error in switch(model, exponential = fit.exponential(v.object, c0 = nugget,  :

  EXPR must be a length 1 vector

Any help to know the cause of the error and avoiding it would be highly appreciated.

Thank you very much
Saubhagya Singh Rathore
PhD Candidate
Civil and Environmental Engineering
Georgia Institute of Technology