[R] nls, restrict parameter values
angel_lul at hotmail.com
Thu May 8 17:38:55 CEST 2003
I posted a question (bellow) a few weeks ago and had a reply (thanks
Christian) that partly solves the problem, but I still would like to be able
to restrict some of the independent variables in a nls model to be always
>0, (is there a way to do it)??
>From: "Christian Ritz" <ritz at dina.kvl.dk>
>To: "Angel -" <angel_lul at hotmail.com>
>CC: <r-help at stat.math.ethz.ch>
>Subject: Re: [R] nls: Missing value or an Infinity produced when evaluating
>Date: Wed, 23 Apr 2003 15:22:37 +0200
>I tried reparametrise your model, setting:
>and giving the following formula in R:
>And this works for me, but the u estimate is negative (not significantly
>different from 0, though).
>----- Original Message -----
>From: "Angel -" <angel_lul at hotmail.com>
>To: <r-help at stat.math.ethz.ch>
>Sent: Wednesday, April 23, 2003 2:29 PM
>Subject: [R] nls: Missing value or an Infinity produced when evaluating the
> > Hi,
> > I am trying to fit a sigmoid curve to some data with nls but I am
> > into some trouble.
> > Seems that the optimization method is getting down to some parameter
> > estimates that make the equation unsolvable. This is an example:
> >> growth<-data.frame(Time=c(5,7,9,11,13,15,17,19,21,23,25,27),BodyMass=c
> >56043.86 : 3.0 2500.0 1.5 >Error in numericDeriv(form[],
>names(ind), env) : > Missing value or an Infinity produced when
>evaluating the model
> >Is there anyway I can restrict the parameter values used so it doesn't
>get to this no return point.
> >Any other alternatives are also very welcome!
> >Thanks in advance,
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