[R-sig-Geo] vgmST parameters
Dr. Benedikt Gräler
b.graeler at 52north.org
Tue Sep 26 10:27:37 CEST 2017
Admittedly, the choice of the initial parameter is not an easy task.
Different models combine the components in a different way. In the
separable model for instance, the spatial and temporal variogram are set
to a joint sill of 1 each where the sill of the entire variogram is a
separate parameter. Contrary, the metric covariance model only has a
single variogram model as input that represents the entire joint sill
where others are a product or the sum of two or three models (see [1]
for details). I wrote a shiny app that is available as source from [2]
and a link to a running instance is listed at [3]. Running the app
locally for one owns empirical variogram might help to identify the
right starting values.
HTH,
Ben
[1]
https://cran.r-project.org/web/packages/gstat/vignettes/spatio-temporal-kriging.pdf
[2] https://github.com/BenGraeler/copulatheque/tree/master/spacetime
[3] http://ben.graeler.org/shiny-apps/
On 25/09/2017 04:44, Mahsa Sameti wrote:
> Dear all
>
> When working with vgmST function, how we choose starting values for space,
> time anf joint vgm?
> If we should choose them from sample stvariogram, why are they different in
> different covariance models? I mean, initial values of space and time vgm in
> separable model is different from sum-metric model. how we choose them?
>
> Thanks alot.
>
> [[alternative HTML version deleted]]
>
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--
Dr. Benedikt Gräler
52°North Initiative for Geospatial Open Source Software GmbH
Martin-Luther-King-Weg 24
48155 Muenster, Germany
E-Mail: b.graeler at 52north.org
Fon: +49-(0)-251/396371-39
Fax: +49-(0)-251/396371-11
http://52north.org/
Twitter: @FiveTwoN
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Local Court Muenster HRB 10849
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