The default argument for varPower's `form' arg is form = ~fitted(.)
I am pretty sure that is the `.' that is not found, and I guess it is an
S/R difference.
I've always had trouble with this form of varPower (even in S). I just
wonder if form = ~fitted(".") might work.
On Thu, 15 Jan 2004, Ravi Varadhan wrote:
> Dear Christian:
>
> That is not the problem, but thanks for your attempted help. I still
> don't know what the problem is. Has anyone encountered this while
> using "gnls" function in the package "nlme"?
>
> thanks again for any help,
>
> Ravi.
>
>
>
> ----- Original Message -----
> From: Christian Mora <[EMAIL PROTECTED]>
> Date: Wednesday, January 14, 2004 7:15 pm
> Subject: RE: [R] Generalized least squares using "gnls" function
>
> > Have you tried removing tol=1.e-07 or changing the value considering
> > that the error is Object "." not found
> >
> > -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] On
> > Behalf Of Ravi Varadhan
> > Sent: Wednesday, January 14, 2004 6:11 PM
> > To: [EMAIL PROTECTED]
> > Subject: [R] Generalized least squares using "gnls" function
> >
> >
> > Hi:
> >
> > I have data from an assay in the form of two vectors, one is
> > response
> > and the other is a predictor. When I attempt to fit a 5 parameter
> > logistic model with "nls", I get converged parameter estimates. I
> > also
> > get the same answers with "gnls" without specifying the "weights"
> > argument.
> >
> > However, when I attempt to use the "gnls" function and try to
> > estimate
> > the variance function, as a power function, I get the following
> > error
> > message:
> >
> > > ans51g <- gnls(log(b51) ~ p0 + p1/(1 + exp(-(log(dose)-
> > p2)/p3))^p4,
> > start=list(p0=3,p1=1,p2=4,p3=2,p4=1.5),control=gnlsControl(tol=1.e-
> > 07),weights=varPower())
> > Error in eval(expr, envir, enclos) : Object "." not found
> > >
> >
> > What am I doing wrong here and how can I do a GLS analysis with a
> > variance function that is estimated from the data?
> >
> > Here is my data:
> >
> > > b51 <- c(17447.60674, 7060.37234, 2872.53012, 796.40426,
> > 454.47222, 260.22340, 120.11905, 83.40196, 51.45745,
> > 36.87912, 26.73256, 25.18681, 17.97674)
> > > dose <- c( 1.000000e+04, 1.000000e+03, 2.500000e+02,
> > 6.250000e+01,
> > 3.125000e+01, 1.562500e+01, 7.812500e+00, 3.906250e+00,
> > 1.953125e+00, 9.765625e-01, 4.882813e-01, 2.441406e-01, 1.000000e-03)
> >
> > thanks for the help,
> > Ravi.
> >
> > ______________________________________________
> > [EMAIL PROTECTED] mailing list
> > https://www.stat.math.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide!
> > http://www.R-project.org/posting-guide.html
> >
> >
>
> ______________________________________________
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>
--
Brian D. Ripley, [EMAIL PROTECTED]
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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