Local spacetime kriging
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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Benedikt Gr?ler 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 -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 560 bytes Desc: OpenPGP digital signature URL: <https://stat.ethz.ch/pipermail/r-sig-geo/attachments/20140515/f3af1bae/attachment.bin>