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

[Edzer Pebesma]

Right, I believe the linear model without sill -- vgm(1, "Lin", 0) --
does work; note that the 1 in this case is a slope, no longer a partial
sill. You may also set the range to a value larger than the maximum
possible distance.

On 07/02/2013 04:16 PM, Tobias Vetter wrote:
> Thank you.
> So as long as all my distances   are smaller than the range I will not
> have this problem?
> Tobias
>> 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
>>>
>>>
>>> _______________________________________________
>>> R-sig-Geo mailing list
>>> R-sig-Geo at r-project.org
>>> https://stat.ethz.ch/mailman/listinfo/r-sig-geo
>>>
> 
> _______________________________________________
> R-sig-Geo mailing list
> R-sig-Geo at r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-geo

-- 
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