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List:       r-help
Subject:    Re: [R] non-linear trends in kriging model
From:       Paulo Justiniano Ribeiro Jr <paulojus () est ! ufpr ! br>
Date:       2003-09-30 12:46:09
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David

Indeed, the trend term in geoR must be a linear one.
You can:
1) fit you model by alternating between using nls() and passing the
residuals to the functions in geoR
or
2) try trying to fit using the functions in the nlme() package

Regards
P.J.

On Tue, 30 Sep 2003, David Pleydell wrote:

> Hi
> I am struggling to fit a non-linear trend using the
> likfit function in geoR.
>
> Specifically I want a sigmoidal function, something
> like SSfpl in the nls package to fit the trend.  But
> it seems trend.spatial in geoR only works with lm or
> glm type models.
>
> Any ideas how I can specify the model to calculate the
> kriging parameters using REML, including the
> parameters of a sigmoidal trend function (such as
> SSfpl)?
>
> Thanks
> David
>
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>

Paulo Justiniano Ribeiro Jr
Departamento de Estatística
Universidade Federal do Paraná
Caixa Postal 19.081
CEP 81.531-990
Curitiba, PR  -  Brasil
Tel: (+55) 41 361 3471
Fax: (+55) 41 361 3141
e-mail: pj@est.ufpr.br
http://www.est.ufpr.br/~paulojus


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