nls not converging for zero-noise cases <Setzer.Woodrow <at> epamail.epa.gov> writes:
> > No doubt Doug Bates would gladly accept patches ... . > The zero-noise case is irrlevant in practice, but quite often I have uttered &/(!! (vituperation filter on) when nls did not converge with real data. The dreaded "min step reduced...". And yet, I found that nls is damned right not to behave nicely in many cases. Recently, a colleague fitted gastric emptying curves using GraphPad, with 100% success, and nls failed for one third of these. When we checked GraphPads output more closely, some of the coefficients looked like 2.1 with a confidence interval in the range -27128 ... 314141. Nobody forces you to look at these, though, when using GraphPad. I only wish nls were a little bit more polite in telling me what went wrong. Dieter ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
