Actually, the data that I used are measurements of plant growth during an entire year.It is usual to model the growth with logistic models. I have already tried the simple logistic model (which works). But the problem is that with this model the inflexion point occurs half-way up or down the logistic curve. Thats why, despite the small amount of measurements, I wanted to try the generalized logistic model proposed by richards.
So I will still try the nls2 package, just in case. And if it doesn't work, I'll use "a more parsimonious model" as you two have suggested. Thank you for your answers -- Nathalie YAUSCHEW-RAGUENES Ph.D Student Unité de Recherches Ecologie Fonctionnelle et Physique de l'Environnement ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
