[R-sig-Geo] maximum likelihood variogram parameter estimation, non-Euclidian distances

[Facundo Muñoz]

  Hi Tim,
I have been in a similar situation, and modified some functions in geoR 
in order to fit variograms, and perform kriging with non-Euclidean 
distances. In particular, you can use likfit() and get 
maximum-likelihood estimates for variogram models with non-Euclidean 
distances.
You can get the modified package (source) from 
http://www.geeitema.org/doc/guenmap//docs/modif.geoR.1.6-27.tar.gz.

Please note that this modifications do not perform positive-definiteness 
checking.
You should do that manually.
That is something I should implement.

Please let me know if you try it, and if you need any help.
ƒacu.-


On 15/07/10 01:24, Timothy W. Hilton wrote:
> Hello R-sig-Geo list,
>
> I want to calculate maximum likelihood estimations for variogram
> parameters (sill, range).  My data locations span North America, thus I
> believe that UTM coordinates (or any other projection) will distort
> distances between sites too much for me to use Euclidian coordinates.
>
> As far as I can tell, geoR will not accept non-Euclidian coordinates or
> allow the user to specify a distance function.  gstat accepts latitude
> and longitude to define locations, but does not include maximum
> likelihood estimation for the range (fit.variogram.reml estimates sill
> only).
>
> Is anyone aware of an R geostats package that handles my situation?
>
> Many thanks!
> Tim
>
> --
>
> Timothy W. Hilton
> PhD Candidate, Department of Meteorology
> The Pennsylvania State University
> 503 Walker Building, University Park, PA   16802
> hilton at meteo.psu.edu
>
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