[R-sig-ME] 'fixed' covariates in nlmer

Laurent Gentzbittel gentz at ensat.fr
Fri Jan 21 09:51:36 CET 2011

Dear Chris,

  I ended with a similar conclusion than yours. Yet, from a scientific 
point of view, the population effects that I would like to add are fixed 

It is really unfortunate that this functionality is not implemented into 
the nlmeR (lme4) function , precluding the use of the package for my 
work. I asked D. Bates but didn't get any answer.
I'm still "surviving" using the nlme package, with all the problems 
related to numerical estimation and convergence. It is not perfect and 
sometimes frustrating, yet it allows results to be analyzed.
I thus need to play with two packages : lme4 for 'simple' linear mixed 
models and nlme for non-linear mixed models.


> Dear Laurent,
> Did you ever get a reply about your message below?
> I am also investigating the same problem.
> My impression is that nlmeR  (lme4) is currently intended
> just for the individual fixed effect estimates and that the population
> values you describe would need
> to be added in the random effects.
> So I think that if for some reason you need these in fixed effects
> rather than random  then we would need to use nlme.
> Is that also your impression and what you
> ended up doing?
> Many thanks
> Cheers
> Chris

Prof. L. GENTZBITTEL            Phone: +33 (0)5 34 32 38 96
INP - Agro Toulouse             Fax  : +33 (0)5 34 32 38 89
18, Chemin de Borde Rouge - Auzeville Tolosane
E-mail:                         gentz at ensat.fr

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