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...m each time. I know that most of the problem comes from the choice of the initial values of the parameters Asym_inf, Asym_inf, n1, n2, tmid1, tmid2, scal1and scal2. My question is how could I estimate those initial values so that the nls fitting works. Thanks in advance -- Nathalie YAUSCHEW-RAGUENES Ph.D Student Unit? 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

...r 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 Unit? 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 T?l : +33 (0)5 57 12 24 31 Fax : +33 (0)5 57 12 24 20 e-mail : nathalie.yauschew-Raguenes at b...