[R-sig-Geo] variogram problem

[Edzer Pebesma]

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.
>>
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>>
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> 
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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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