[R] How do I back transforme ordinary log-krigged prediction values?

[Zia Uddin Ahmed]

Farrar,

I did ordinary kriging (OK) after log10 transformation. I need to
backtransfer my predicted data to original unit. You are right! Anti-log
of the predictions for bcaktransformation might give biased values. For
minimize the biasness, it is necessary know the lagrange-multiplier (y)
and prediction error (s).

"We can not just exponentiate the estimate, because the estimate is a
weighted sum(not product!) of logarithms".

This is the  formula for back-transformation  OK predictions:
Z(~x0) = e{ˆY (~x0)+s2OK(~x0)/2-y}

I do not know, how to extract lagrange-multiplier  after OK prediction in
gstat in R.


Thanks

Zia

>
>   Zia,
>   I'm not an expert on Kriging, or on the particular package.  It sounds
> like you just want to know how to anti-log the predictions,. which
> shouldn't be hard.  However, depending on what you actually need to
> predict, it seems your predictions might be biased, right?
>
> regards,
>   Farrar
>
>
> Zia Uddin Ahmed <zua3 at cornell.edu> wrote:
>   I have a question to everybody.
>
> After log10 transfprmation, I have done ordinary kriging in gstat in R? I
> need to back trnasform the prediction values to orgiginal scale. How do I
> do this in gstat in R?
>
> Thanks
>
> Zia
> --
> Zia Uddin Ahmed
> 915 Brad Field Hall
> Department of Crop and Soil
> Cornell University
> Ithaca NY 14850
> USA
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>


--
Zia Uddin Ahmed
915 Brad Field Hall
Department of Crop and Soil
Cornell University
Ithaca NY 14850
USA