mykrige.cv = gstat:::krige.cv.spatial
mykrige.cv = edit(mykrige.cv)
then, you will find out that you will have to do the same with gstat.cv,
and that gstat.cv is rather cryptic as it deals with cokriging of which
ordinary kriging is a special case.
Maybe it wasn't such a good idea after all if you're new to R, sorry.
Tobin Cara wrote:
Hello Prof. Pebesma,
I would like to use leave-one-out cross validation to have a fair comparison with my other methods.
Could you explain further how to copy krige.cv to my own function and modify?
Can I open up the krige.cv code somewhere? I am still new to R.
Thank you in advance,
Cara
________________________________________
De : Edzer Pebesma [edzer.pebe...@uni-muenster.de]
Date d'envoi : vendredi, 15. janvier 2010 12:14
À : Tobin Cara
Cc : r-sig-geo@stat.math.ethz.ch
Objet : Re: [R-sig-Geo] Inverse Distance Weighting and Treating kriged data
before cross validation
Dear Cara,
one way would be to copy krige.cv to your own function and modify this;
I would recommend this if you want leave-one-out cross validation.
If n-fold cross validation is good enough for a few folds, e.g. because
you have plenty of data, then I would do the whole procedure "manually",
using predict, krige or idw on the points of a particular fold using the
data from the remaining folds.
--
Edzer
Tobin Cara wrote:
Hello,
I am using inverse distance weighting with gstat for temperature just to
compare it with other kriging methods. For a temperature field, I have removed
the elevation effect at the stations by normalizing all stations to the lowest
with a lapse rate of -6.5 deg C /1000 m.
Now, I want to krig the normalized data and then add back the lapse rate
multiplied by the difference in elevation to get the real temperatures at all
real elevations. However, how can I do this before cross validation?
I only know cross validation with the following command where it does not allow
manipulation of the kriged field before cross validation:
crossval_idw <- krige.cv(Temp93hr~1, DataCoordhr)
Thank you in advance for your help.
Cheers,
Cara
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--
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics e.pebe...@wwu.de
--
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of Münster
Weseler Straße 253, 48151 Münster, Germany. Phone: +49 251
8333081, Fax: +49 251 8339763 http://ifgi.uni-muenster.de
http://www.52north.org/geostatistics e.pebe...@wwu.de
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