From nikko at hailmail.net  Thu Oct 18 16:17:50 2007
From: nikko at hailmail.net (Nicholas Lewin-Koh)
Date: Thu, 18 Oct 2007 10:17:50 -0400
Subject: [Rd] nmle: gnls freezes on difficult case
Message-ID: <1192717070.9380.1216571837@webmail.messagingengine.com>

Hi,
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?

Nicholas


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:
    power 
0.3373206 

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

Convergence:
   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



[Rd] nmle: gnls freezes on difficult case
Nicholas Lewin-Koh