[R-sig-Geo] Local spacetime kriging

[Benedikt Gräler]

On 15.05.2014 15:47, Edzer Pebesma wrote:
> On 05/15/2014 10:58 AM, Roelof Coster wrote:
>> Also, in case kriging in a neighbourhood is possible, how does the function
>> determine this neighbourhood? How is distance in space compared to distance
>> in time?
> 
> It uses http://cran.r-project.org/web/packages/FNN/index.html
> to get nearest neighbours, and, unless parameter stAnis is specified,
> tries to figure out a sensible space/time anisotropy from the variogram
> model. The source is found
> https://r-forge.r-project.org/scm/viewvc.php/pkg/R/krige0.R?view=markup&root=gstat
> and look for function krigeST.local

The "closest" neighbours are the "strongest" correlated ones. To achieve
this, a larger (4-fold by default) metric spatio-temporal neighbourhood
with some spatio-temporal anisotropy (stAni or from the variogram model)
is selected. For these neighbours, the spatio-temporal covariance
function is evaluated and the ones with the strongest correlation are
selected. The interpolation is then carried out using these nmax
neighbours.

HTH,

 Ben


> 
> The curent version on CRAN does not pass through parameters
> checkNeighbourhood and bufferNmax, just corrected this on r-forge.
> 
> Wbr,
> 
>>
>> Thanks! Roelof Coster
>>
>> 	[[alternative HTML version deleted]]
>>
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> 
> 
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-- 
Benedikt Gräler

ifgi - Institute for Geoinformatics
University of Muenster

http://ifgi.uni-muenster.de/graeler

Phone: +49 251 83-33082
Mail: ben.graeler at uni-muenster.de

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