[R] nonlinear least square fit of a known function

Peter Dalgaard BSA p.dalgaard at biostat.ku.dk
Fri Oct 25 16:22:11 CEST 2002

Douglas Bates <bates at stat.wisc.edu> writes:

> John Fox <jfox at mcmaster.ca> writes:
> > Dear Andy and Dave,
> > 
> > The nls documentation indicates that weights aren't (yet) implemented.
> > 
> > Regards,
> >   John
> But there is an example in the documentation, contributed by Martin
> Maechler, showing how to do weighted nonlinear least squares.

And of course multiplying both sides of a model formula with the
square root of the weights is not going to make the model any more nor
less nonlinear. (But predicting and such requires a little care).
Actually Martin's example is slightly different from what weights=w
would do since his weights depend on the predictor.

Still, a weights argument would be nice. Could we have one for 1.7.0?
Any inklings about how hard it would be to implement?


   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
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