[R] comparison of parameters for nonlinear regression

[Nathalie Yauschew-Raguenes]

Hi,

I have two series of data set (it's measurment of growth but under two 
different conditions).
To model these data I use the same function which is :

formula <- y ~ Asym_inf  + Asym_sup * ( (1 / (1 + (n1 * (exp( (tmid1-x) 
/ scal1) )^(1/n1) ) ) ) - (1 / (1 + (n2 * (exp( (tmid2-x) / scal2) 
)^(1/n2) ) ) ) )

After the estimation of the parameters thanks to "nls", I have 2 models.
The idea is I want to compare this 2 models and particularly I want to 
know if the parameters are different are not beteween this 2 models. Is 
there a way to do it simply in R?

Thanks in advance

-- 
Nathalie YAUSCHEW-RAGUENES
Ph.D Student

Unité de Recherches Ecologie Fonctionnelle et Physique de l'Environnement (EPHYSE)
INRA, Centre de Bordeaux - Aquitaine
71 Av Edouard Bourlaux
33883 Villenave d'Ornon Cedex
France

Tél : +33 (0)5 57 12 24 31
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e-mail : nathalie.yauschew-Raguenes at bordeaux.inra.fr