[R-sig-Geo] variogram problem

[adeela uaf]

This is the the data set and want to make variogram for Cd15. The distance
between each sample location was 4 cross 4 km. Please suggest me how to
allocate initial guess about nugget, sill and range parametrs. Moreover, I
have used log transformation for my variable Cd15. Is it appropriate? Or
there is any other transformation for this.
Thanks,
Regards
Adeela

On Wed, Jun 24, 2015 at 7:08 PM, Edzer Pebesma <
edzer.pebesma at uni-muenster.de> wrote:

> Thierry is right about that; without that we can only guess, which is
> what I will do now.
>
> fit.variogram does a non-linear fit using some steepest descent method,
> and needs initial values for that. The initial values you provide are 1
> (partial sill), 5 (range), and 1 (nugget). In case v does not provide
> good information on how to improve these initial values, e.g. because 5
> is smaller than the smallest distance in it, it can't figure out where
> to go in order to improve. This means it got stuck, and gives this
> warning. The plot
>
> plot(v, vgm(1, "Sph", 5, 1))
>
> will reveal the problem to you (and to us, if you'd share it).
>
> On 06/24/2015 03:42 PM, Thierry Onkelinx wrote:
> > You'll need to provide a reproducible example. Your code is not
> > reproducible without the data.
> >
> > ir. Thierry Onkelinx
> > Instituut voor natuur- en bosonderzoek / Research Institute for Nature
> and
> > Forest
> > team Biometrie & Kwaliteitszorg / team Biometrics & Quality Assurance
> > Kliniekstraat 25
> > 1070 Anderlecht
> > Belgium
> >
> > To call in the statistician after the experiment is done may be no more
> > than asking him to perform a post-mortem examination: he may be able to
> say
> > what the experiment died of. ~ Sir Ronald Aylmer Fisher
> > The plural of anecdote is not data. ~ Roger Brinner
> > The combination of some data and an aching desire for an answer does not
> > ensure that a reasonable answer can be extracted from a given body of
> data.
> > ~ John Tukey
> >
> > 2015-06-24 15:23 GMT+02:00 adeela uaf <adeela.uaf at gmail.com>:
> >
> >> Hi,
> >> Can anybody help me in fitting variogram in gstat package in R. I am
> trying
> >> but having this problem. Where Cd15 is the amount of Cadmium in soil at
> 15
> >> cm depth.
> >> v<-variogram(Cd15~1,data)
> >> v.fit<-fit.variogram(v,vgm(1,"Sph",5,1))
> >> Warning message:
> >> In fit.variogram(v, vgm(1, "Sph", 5, 1)) :
> >> Warning: singular model in variogram fit
> >> ******************************
> >> Adeela
> >> University of Agriculture Faisalabad
> >> Department of Math & Stat.
> >>
> >>         [[alternative HTML version deleted]]
> >>
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> >> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> >>
> >
> >       [[alternative HTML version deleted]]
> >
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> >
>
> --
> Edzer Pebesma
> Institute for Geoinformatics (ifgi),  University of Münster,
> Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
> Journal of Statistical Software:   http://www.jstatsoft.org/
> Computers & Geosciences:   http://elsevier.com/locate/cageo/
> Spatial Statistics Society http://www.spatialstatistics.info
>
>
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