[R-sig-ME] nlme optim control option

Stephan Moratti moratti at med.ucm.es
Tue Apr 29 13:05:21 CEST 2008


I am using the nlme package for quite a while, but recently I have 
discovered the "optim" option in the lmeControl function and I have read 
that until the R verison 2.2.0 the optimization function is "nlminb" and 
before it was "optim" by default. As I am a "user" of R I am not into 
the optimization functions. However, I have a case now where with optim 
= "nlminb" the model does not converge, whereas with optim = "optim" the 
model converges.

Can somebody explain to me in easy words what the difference is ? If 
nlminb does not converge, but optim does, is the result less trustable ?



*Stephan Moratti, PhD/
/**/see also: http://web.mac.com/smoratti/
/*Centro de Tecnología Biomédica CBT,
Universidad Politécnica de Madrid,

en la actualidad (currently at) en el
Centro de Magnetoencefalografía Dr. Perez Modrego,
Universidad Complutense de Madrid,
Faculdad de Medicina,
Pabellón 8,
Avda. Complutense, s/n,
28040 Madrid,

email: moratti at gbt.tfo.upm.es <mailto:moratti at gbt.tfo.upm.es>
         moratti at med.ucm.es
Tel.:    +34 91 394 2292
Fax.:   +34 91 394 2294

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