[Rd] nmle: gnls freezes on difficult case

From: Nicholas Lewin-Koh <nikko_at_hailmail.net>
Date: Thu, 18 Oct 2007 10:17:50 -0400

Following up on my own post, if in gnlsControl I specify opt='optim' gnls exits quite nicely, with an error, which is what I would expect. Is this a bug in nlminb?


tt<-gnls(response~SSllogis(conc,A,B,xmid,scal),tdat,start=start,weights=varPower(),verbose=TRUE,control=gnlsControl(opt='optim')) **Iteration 1
GLS step: Objective: 29.04254varStruct parameters:


NLS step: RSS = 0
 model parameters:-0.799941 8.99983 -0.522623 212.314  iterations: 2


   params varStruct
 1.172208 1.000000
Error in optim(c(coef(gnlsSt)), function(gnlsPars) -logLik(gnlsSt, gnlsPars), :
  initial value in 'vmmin' is not finite In addition: Warning messages:

1: In log(xmid) : NaNs produced
2: In log(xmid) : NaNs produced
3: In log(xmid) : NaNs produced

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