[R] Estimates with lme(...varPower())

Dieter Menne dieter.menne at menne-biomed.de
Tue Apr 29 16:50:41 CEST 2003

Dear Douglas Bates,

> It would be more common to use the predicted response rather than the
> observed response for the varPower weights, as in
>  varPower(form = ~fitted(.))

Following the example on page 223 of PB, I had used that first, but did not
achieve convergence. Will try with more iterations.

> If you use the observed responses then abnormally low observed
> responses will have unusually high weights in the fit, leading to low
> predictions, as you observed.

Dieter Menne

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