[R] Cross validation for Ordinary Kriging

[Jon Olav Skoien]

Pearl,

The error suggests that there is something wrong with x2, and that there 
is a difference between the row names of the coordinates and the data. 
If you call
str(x2)
see if the first element of @coords is different from NULL, as this can 
cause some problems when cross-validating. If it is, try to figure out 
why. You can also set the row.names equal to NULL directly:
row.names(x2 at coords) = NULL
although I dont think such manipulation of the slots of an object is 
usually recommended.

Cheers,
Jon

BTW, you will usually get more response to questions about spatial data 
handling using the list r-sig-geo 
(https://stat.ethz.ch/mailman/listinfo/r-sig-geo)


On 1/6/2011 4:00 PM, pearl may dela cruz wrote:
> ear ALL,
>
> The last part of my thesis analysis is the cross validation. Right now I am
> having difficulty using the cross validation of gstat. Below are my commands
> with the tsport_ace as the variable:
>
> nfold<- 3
> part<- sample(1:nfold, 69, replace = TRUE)
> sel<- (part != 1)
> m.model<- x2[sel, ]
> m.valid<- x2[-sel, ]
> t<- fit.variogram(v,vgm(0.0437, "Exp", 26, 0))
> cv69<- krige.cv(tsport_ace ~ 1, x2, t, nfold = nrow(x2))
>
> The last line gives an error saying:
> Error in SpatialPointsDataFrame(coordinates(data),
> data.frame(matrix(as.numeric(NA),  :
>    row.names of data and coords do not match
>
> I don't know what is wrong. The x2 data is a SpatialPointsdataframe that is why
> i did not specify the location (as it will take it from the data). Here is the
> usage of the function krige.cv:
>
> krige.cv(formula, locations, data, model = NULL, beta = NULL, nmax = Inf,
>          nmin = 0, maxdist = Inf, nfold = nrow(data), verbose = TRUE, ...)
> I hope you can help me on this. Thanks a lot.
> Best regards,
> Pearl
>
>
>
>
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