[R] specifying starting values in nlsList/conversion problems

About this list Date view Thread view Subject view Author view Attachment view

From: Schmidt.Matthias (FORST) (Matthias.Schmidt@forst.bwl.de)
Date: Thu 27 May 2004 - 23:10:00 EST


Message-id: <855D381F618DE84FA58C035BA803FCE6B9A723@fvafr-se1.forst.bwl.de>

Hi
I am using nlsList from the nlme package to estimate group specific
coefficient sets to get a first impression of the structure of coefficients
in relation to potential predictor variables. In some cases I got
coefficients in other there are conversion problems due to bad start values
I guess, resulting in typical error messages as known from nls:

Error in nls(formula = formula, data = data, start = start, control =
control) :
        singular gradient
Error in nls(formula = formula, data = data, start = start, control =
control) :
        step factor 0.000488281 reduced below `minFactor' of 0.000976563
Error in numericDeriv(form[[3]], names(ind), env) :
        Missing value or an Infinity produced when evaluating the model

is there a possibility to specifiy group specific starting or an algorithm
which tests a matrix of starting with a certain stepwidth to overcome the
conversion problems?

thanx for help

***********************************************************
Matthias Schmidt
Forstliche Versuchs- und Forschungsanstalt Baden-Württemberg (FVA)
Abteilung Biometrie und Informatik
Wonnhaldestr. 4
79100 Freiburg i. Br
Tel.: + 49 (0)761 / 4018 -187
Fax: + 49 (0)761 / 4018 - 333

______________________________________________
R-help@stat.math.ethz.ch 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


About this list Date view Thread view Subject view Author view Attachment view

This archive was generated by hypermail 2.1.3 : Mon 31 May 2004 - 23:05:13 EST