[R] skip non-converging nls() in a list

[Andrew Robinson]

Hi Marc,

use try()

Cheers

Andrew

On Mon, Feb 18, 2008 at 01:45:35PM -0500, Marc Belisle wrote:
> Howdee,
> 
> My question appears at #6 below:
> 
> 1. I want to model the growth of each of a large number of individuals using
> a 4-parameter logistic growth curve.
> 
> 2. nlme does not converge with the random structure that I want to use.
> 
> 3. nlsList does not converge for some individuals.
> 
> 4. I decided to go around nlsList using:
> 
> t(sapply(split(data, list(data$id)),
>     function(subd){coef(nls(mass ~ SSfpl(age, A, B, xmid, scal), data =
> subd))}))
> 
> 5. This does not converge either:
> 
> 'Error in nls(y ~ cbind(1, 1/(1 + exp((xmid - x)/exp(lscal)))), data = xy,
> :
>         singular gradient'
> 
> 6. Would anyone know if I can get R to skip non-converging use of nls() so
> that I can at least obtain the parameters for the curves which R can fit?
> 
> Thanks for your time,
> 
> Marc
> 
> ===================
> Marc B?lisle
> Professeur adjoint
> Chaire de recherche du Canada en ?cologie spatiale et en ?cologie du paysage
> D?partement de biologie
> Universit? de Sherbrooke
> 2500 Boul. de l'Universit?
> Sherbrooke, Qu?bec
> J1K 2R1 Canada
> 
> T?l: +1-819-821-8000 poste 61313
> Fax: +1-819-821-8049
> Courri?l: Marc.M.Belisle at USherbrooke.ca
> 
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-- 
Andrew Robinson  
Department of Mathematics and Statistics            Tel: +61-3-8344-6410
University of Melbourne, VIC 3010 Australia         Fax: +61-3-8344-4599
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