Re: [R] error using nls with logistic derivative

2012-04-17 Thread Francisco Mora Ardila
It seems to work! Thanks and sorry for the personal message Francisco On Tue, 17 Apr 2012 09:09:24 +0200, peter dalgaard wrote > On Apr 17, 2012, at 06:23 , Francisco Mora Ardila wrote: > > > Hi > > > > I´m trying to fit a nonlinear model to a derivative of the logistic function > > > > y = a

Re: [R] error using nls with logistic derivative

2012-04-17 Thread John C Nash
Peter Dalgaard has already given some indications. However, nls() is pretty fragile as a solver in my experience. I'm in the process of putting some more robust (in the computing and not statistical sense) solvers in the nlmrt package on the R-forge project at https://r-forge.r-project.org/R/?g

Re: [R] error using nls with logistic derivative

2012-04-17 Thread Gabor Grothendieck
On Tue, Apr 17, 2012 at 12:23 AM, Francisco Mora Ardila wrote: > Hi > > I´m trying to fit a nonlinear model to a derivative of the logistic function > > y = a/(1+exp((b-x)/c)) (this is the parametrization for the SSlogis function > with nls) > > The derivative calculated with D function is: > >>

Re: [R] error using nls with logistic derivative

2012-04-17 Thread peter dalgaard
On Apr 17, 2012, at 06:23 , Francisco Mora Ardila wrote: > Hi > > I´m trying to fit a nonlinear model to a derivative of the logistic function > > y = a/(1+exp((b-x)/c)) (this is the parametrization for the SSlogis function > with nls) > > The derivative calculated with D function is: > >> l