R help - Jul 2005 - problem in Krig function of "Fields" package

hello

I try to build DEM  using Krig function of fields package.
And I get this error message.
here is the procedure I followed:

 >
dt<-read.table("/usr/local/bartin/stat/topostat1",header=F,sep="|")
 > names(dt) <-c("x","y","z")
 > coord<-cbind(dt$x,dt$y)
 > elevation<-cbind(dt$z)
 >
fit1<-Krig(coord,elevation,cov.function=exp.cov,scale.type="range")
[1] "condition number is 907405545.878743"
Error in Krig(kord, el, cov.function = exp.cov, scale.type = "range")
:
        Covariance matrix is close
to
singular

here is the structure  of my data:

`data.frame':   3911 obs. of  3 variables:
 $ x: num  50139 50169 50214 50223 50227 ...
 $ y: num  4592999 4593322 4593054 4593151 4593246 ...
 $ z: int  320 320 320 320 320 320 320 320 320 320 ...

what do you suggest to solve the problem ?

kind regards



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My guess is that you have two data points which are very close together.
The normal way out is to included a nugget effect in your model, but it 
can also be appropriate to leave out one of a pair of points.

On Tue, 19 Jul 2005, orkun wrote:
> hello
>
> I try to build DEM  using Krig function of fields package.
> And I get this error message.
> here is the procedure I followed:
>
> >
dt<-read.table("/usr/local/bartin/stat/topostat1",header=F,sep="|")
> > names(dt) <-c("x","y","z")
> > coord<-cbind(dt$x,dt$y)
> > elevation<-cbind(dt$z)
> >
fit1<-Krig(coord,elevation,cov.function=exp.cov,scale.type="range")
> [1] "condition number is 907405545.878743"
> Error in Krig(kord, el, cov.function = exp.cov, scale.type =
"range") :
>        Covariance matrix is close
> to
> singular
>
> here is the structure  of my data:
>
> `data.frame':   3911 obs. of  3 variables:
> $ x: num  50139 50169 50214 50223 50227 ...
> $ y: num  4592999 4593322 4593054 4593151 4593246 ...
> $ z: int  320 320 320 320 320 320 320 320 320 320 ...
>
> what do you suggest to solve the problem ?
>
> kind regards
>
>
>
> ______________________________________
> XamimeLT - installed on mailserver for domain @deprem.gov.tr
> Queries to: postmaster at deprem.gov.tr
> ______________________________________
> The views and opinions expressed in this e-mail message are ...{{dropped}}
>
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>
-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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