[R] NLS estimation: Starting values
Prof Brian Ripley
ripley at stats.ox.ac.uk
Fri Oct 24 16:42:44 CEST 2003
optim() needs starting values too, but *may* be more robust than nls to
their specification ....
On Fri, 24 Oct 2003, Giovanni Caggiano wrote:
> I am trying to fit to the data a nonlinear function, say z(tau;b) where tau
> is the independent variable and b is 3x1 vector of parameters. Following
> previous suggestions from the list, I am trying to find some "optimal"
> starting values for the three parameters by using the command 'optim' and
> then feed these values to nls for estimation. Does anybody know hot to use
> 'optim' for this purpose?
--
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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