On Mon, Nov 12, 2007 at 04:27:26PM -0300, Horacio Castellini wrote: > Hi all, I'd like fit this function: > > G(t)=A*1/(1+t/B)*1/sqrt(1+t/C) > > where A, B and C are fitting constants that one like search. I have > got a fcs<-(t,G(t)) value table in a data frame. > > Any one can help me? Tahnks Horacio.
if your data are in `df' and the columns are labeled `t' and `G' this seems what you want (cf. `?nls'): nls(G ~ A*1/(1+t/B)*1/sqrt(1+t/C), start =list(A=1, B=2, C=3), data = df) where `start' should be set to reasonable start values. and I would think, it is better to use p1 = 1/B, p2= 1/C during the fit (no singularities of G for certain parameter values...). joerg ______________________________________________ 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.