From: Douglas Bates <dmbates_at_gmail.com>

Date: Sat 20 Aug 2005 - 08:48:28 EST

R-help@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 Received on Sat Aug 20 08:57:40 2005

Date: Sat 20 Aug 2005 - 08:48:28 EST

On 8/19/05, François Morneau <francois.morneau@cirad.fr> wrote:

> Le 11:12 19/08/2005,Douglas Bates écrit:

*> >On 8/18/05, François Morneau <francois.morneau@cirad.fr> wrote:
**> > > Hello,
**> > >
**> > > I want to fit a Gompertz model for tree diameter growth that depends on a 4
**> > > levels edaphic factor ('Drain') and I don't manage to introduce the factor
**> > > variable in the formula.
**> > > Dinc is the annual diameter increment and D is the Diameter.
**> > >
**> > > >treestab
**> > > > Dinc D Drain
**> > > [1,] 0.03 26.10 2
**> > > [2,] 0.04 13.05 1
**> > > [3,] 0.00 24.83 1
**> > > [4,] 0.00 15.92 4
**> > > [5,] 0.00 12.25 4
**> > > [6,] 0.00 11.78 4
**> > > [7,] 0.00 16.87 4
**> > > [8,] 0.00 15.12 4
**> > > [9,] -0.01 13.53 4
**> > > [10,] 0.04 16.55 3
**> > > [11,] 0.025 16.07 3
**> > > [12,] 0.00 30.24 3
**> > > [13,] 0.06 15.28 2
**> > > etc…
**> > > >contrasts(Drain)<-contr.sum(4)
**> > > >mymodel<-nls(Dinc~r*(1+Drain)*D*log(Asym/D), data=treestab,
**> > start=list(r=0.05,
**> > > Asym=40))
**> > >
**> > > Error in numericDeriv(form[[3]], names(ind), env) :
**> > > Missing value or an infinity produced when evaluating the model
**> > > In addition: Warning messages:
**> > > 1: + not meaningful for factors in: Ops.factor(1, Drain)
**> > > 2: + not meaningful for factors in: Ops.factor(1, Drain)
**> >
**> >It is not clear to me what you are trying to do. Can you give us a
**> >bit more information such as how many parameter estimates you expect
**> >to obtain and what they would represent?
**>
**> I'm trying to estimate the effect of the edaphic factor 'Drain' on tree
**> diameter growth. The relationship between diameter 'D' and diameter
**> increment 'Dinc' follow a Gompertz model written : Dinc= r D log(Asym/D)
**> where 'r' is a parameter related to growth speed and 'Asym' is the diameter
**> max where growth stops.
**>
**> My hypothesis is that 'Asym' doesn't change according to edaphic condition
**> but 'r' does. So I'd like to estimate 'Asym' and four 'r'i parameters for
**> each level i of 'Drain' with 'r'i= r0 + effect of 'Drain'i
**>
**> I hope this is helpful...
*

Yes, it is.

*>
**> > >
*

> > > Do I need to use another function instead of nls to correctly include the

*> > > factor 'Drain' ?
**> > >
**> > > Thanks,
**> > >
**> > > François
**>
**> François Morneau
**> UMR Écologie des Forêts de Guyane
**> Kourou, French Guiana
**>
*

>

R-help@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 Received on Sat Aug 20 08:57:40 2005

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