Cross validation for Ordinary Kriging

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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