[R] nlme and pnlsTol
dieter.menne at menne-biomed.de
Fri Dec 10 11:11:01 CET 2004
I do a fit fo a 3-parameter fit to physiological data with nlme:
The approach described in Pinheiro/Bates by using nlsList
as a first approximator was somewhat unstable (many NA), but
a direct fit converges quickly and fits look good:
However, I had to use a rather large value of pnlsTol of 0.1 go achieve
1) What is the price I have to pay when using so large pnlsTol? Could I miss
any more distant optima?
2) When using an even larger value of pnlsTol=0.3, AIC is lower by 2 and
standard errors are somewhat lower. Can I trust this result?
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