[R-sig-Geo] Bug in surf.ls (spatial package)?

[ONKELINX, Thierry]

Dear listers,

When fitting a trend surface I noticed that surf.ls() generates other
values for the model parameters than an ordinary lm(). Since both fit,
in my opinion, the same model to the same data. So I would suppect that
both would generate the same parameter values. Or am I missing
something?

Some sample code.

library("gstat")
data(jura)
library("spatial")
surface.surf <- surf.ls(np = 1, x = prediction.dat$Xloc, y =
prediction.dat$Yloc, z = prediction.dat$Ni)
surface.lm <- lm(Ni ~ Xloc + Yloc, data = prediction.dat)
surface.surf$beta

[1] 18.828803  4.823595 -2.375896

surface.lm$coef

(Intercept)        Xloc        Yloc 
 15.5140337   2.2466673  -0.9299007 

Thanks,

Thierry

------------------------------------------------------------------------
----
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek / Reseach Institute for Nature
and Forest
Cel biometrie, methodologie en kwaliteitszorg / Section biometrics,
methodology and quality assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
Thierry.Onkelinx at inbo.be
www.inbo.be 

Do not put your faith in what statistics say until you have carefully
considered what they do not say.  ~William W. Watt
A statistical analysis, properly conducted, is a delicate dissection of
uncertainties, a surgery of suppositions. ~M.J.Moroney