trend surface analysis

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trend surface analysis

Carlos Henrique Grohmann de Carvalho
Hello,

What is the better way to perform trend surface analysis in R (with GRASS data),
with third-order surfaces (or higher levels?)

thanks
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        Carlos Henrique Grohmann - Guano  
    Geologist - MSc Student at IGc-USP - Brazil
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trend surface analysis

Roger Bivand
Administrator
On Sun, 14 Dec 2003, Carlos Henrique Grohmann wrote:

> Hello,
>
> What is the better way to perform trend surface analysis in R (with GRASS data),
> with third-order surfaces (or higher levels?)

Almost certainly surf.ls() in the spatial package, because it transforms
the coordinates internally to lie within -1, +1. So numerically it will be
more stable than say higher powers of numbers of metres south or north of
the Equator in UTM. Some thought is need to get the points of the
prediction grid right for GRASS, though; see the trmat.G() wrapper
function.

Roger

>
> thanks
>

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Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: Roger.Bivand at nhh.no



Roger Bivand
Department of Economics
Norwegian School of Economics
Helleveien 30
N-5045 Bergen, Norway