[R-sig-Geo] Huge kriging weights when using kriging with external drift in gstat

[Edzer Pebesma]

Tobias, try using another variogram model: the linear model with sill is
not positive definite in more than one dimension (and yes: a warning
about this would have been very nice!)

On 07/02/2013 03:37 PM, Tobias Vetter wrote:
> Dear  all,
> I am interpolating automatically  daily air temperature values using
> kriging with external drift (altitude) and the library gstat. From time
> to time (quite random) I get unrealistic predictions like -400°C with
> very high kriging weights   like 2000.
>  Looking at the data everything seems to be ok.  Then I changed the
> variogram ranges  a little bit and the problem disappears.
> How can this behavior be explained?
> 
>  I  have attached a small  example script for demonstration  and some data.
> 
> Thanks you
> Tobias
> 
> 
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-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
83 33081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de