[R-sig-ME] Port algorithm in nls

[Luis Orlindo Tedeschi]

Folks, I'd like to hear comments about a statement in the help and manual of
R 2.7 about the port algorithm in the nls function.

It says: "The algorithm = "port" code appears unfinished, and does not even
check that the starting value is within the bounds. Use with caution,
especially where bounds are supplied."

IF, and only IF, it is unfinished how reliable are the estimates of the
parameters and why does R 2.7 have it?

It sounds confusing to me... Mainly because most of my fittings are done
with port and I do use the bound statement. Sometimes port is faster than
Gauss-Newton... but now I am confused.

I tried to get more info in Bates and Chambers (1993) but I could not find
it clearly.

Any suggestions?

Thanks in advance...

Luis

______________________________________
Luis Orlindo Tedeschi, PhD, PAS
Assistant Professor
Texas A&M University
230 Kleberg Center
2471 TAMU
College Station, TX 77843-2471
Phone: (979) 845-5065
Fax: (979) 845-5292
Email: luis.tedeschi at tamu.edu
Web: http://nutritionmodels.tamu.edu
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