How to do cross validation for universal krigingin Gstat

Kai Zhang wrote:

Hi Edzer,

Thanks for your quick reply. The primary variable of my interest is 
temperature.  I tried to use krige.cv before, but it did not work. 
The problem arises because the temperature and impervious surface are 
from two files. For universal kriging, the krige function has a 
parameter called "newdata" which handles the second data file. 
However, the krige.cv does not include a "newdata" parameter 
according to the help document. There is a error when I specified two 
datasources when I was running krige.cv in specifying a newdata 
source:    

krige only works when the secondary variable (ELE) is present both in 
the data and in the newdata argument. krige.cv only uses the data 
argument, where ELE is present.

dtw.vgm <- variogram(Temp~ Ele, TMP)
dtw.fit <- fit.variogram(dtw.vgm, model = vgm(1.45, "Exp", 9502,0))
uk.kriged.am <- krige.cv(Temp~Ele,data=TMP,newdata=IMP,model=dtw.fit)
    

Error in function (classes, fdef, mtable)  :   unable to find an 
inherited method for function "krige.cv", for signature "formula", 
"missing"
  

I tried to delete parameters names such as 'data' and 'newdata' 
according to your response to a related problem before in the 
R-sig-Geo archives. However, it still did not work.
 

The krige.cv documentation does not mention a newdata argument. Pls try:

uk.kriged.am <- krige.cv(Temp~Ele, TMP, dtw.fit)

Thanks,
Kai Zhang



======= 2010-02-21 11:51:45 You wrote =======

 

Kai,

krige.cv(Temp~Ele, data, model)

should do the job, assuming that your primary variable of interest is
temperature.
-- 
Edzer


Kai Zhang wrote:
   

Dear all,

I am attempting several Kriging methods to interpolate temperature 
in a area. It works well for me to use krige.cv to conduct cross 
validation for ordinary kriging and gstat.cv for co-kriging. 
However, I am confused on how to conduct cv for universal kriging. 
The temperature data is from the data file 1 and the secondary 
variable with more intense sampling is from another file. Krige.cv 
does not provide a parameter on 'newdata'. When I was trying 
gstat.cv, the variogram function automatically fits cross-variogram 
after I incorporate both temperature and the secondary information 
into a gstat object. Any suggestions are welcome.

g <- gstat(NULL,id="Temp", formula=Temp~1, data=TMP)
g <- gstat(g,id="Ele", formula=Ele~1, data=ELE)
g <- gstat(g, id = "Temp", model = vgm(1, "Exp", 44559, 1))
x <- variogram(g)

Many thanks,
Kai Zhang

-- 
Edzer Pebesma
Institute for Geoinformatics (ifgi), University of M?nster Weseler 
Stra?e 253, 48151 M?nster, Germany. Phone: +49 251 8333081, Fax: +49 
251 8339763  http://ifgi.uni-muenster.de 
http://www.52north.org/geostatistics      e.pebesma at wwu.de

    

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