Prof Brian D Ripley
ripley at stats.ox.ac.uk
Mon Feb 10 10:33:03 CET 2003
Don't use nls for exact fits, as that's not what it is intended for, and
you are trying to achieve a fit to machine accuracy with rounding errors.
You will find several discussions of this in the archives.
On Mon, 10 Feb 2003, Gregory BENMENZER wrote:
> I want to estimate parameters of the model y=a/x with x=1:10 and y=3/x.
> I tested the NLS function.
> Could you tell me why it doesn't converge ?
> Grégory Benmenzer
> > x=1:10
> > y=3/x
> > nls(y~a/x, start=list(a=2), control=nls.control(maxiter=100))
> Error in nls(y ~ a/x, start = list(a = 2), control = nls.control(maxiter = 100)) :
> number of iterations exceeded maximum of 100
Brian D. Ripley, ripley at stats.ox.ac.uk
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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