[R-sig-ME] [R] linear mixed model required for the U.S. FDA

[Helmut Schütz]

Dear Thierry,

Thierry Onkelinx wrote on 2019-08-19 13:00:

> […] The model does not converge on my machine.
>
> library(nlme)
> model2 <- lme(log(PK) ~ period + sequence + treatment , random = ~ 
> treatment | subject, data = data, weights = varIdent(~treatment))

Switching the optimizer from the default "nlminb" to the old one "optim" 
did.

mod  <- lme(log(PK) ~ period + sequence + treatment,
                       random = ~ treatment | subject,
                       data = data, weights = varIdent(~ treatment),
                       method = "REML", na.action = na.exclude,
                       control = list(opt = "optim"))

Now I get a CI of 1.0710967-1.2518824 which is slightly more 
conservative than 1.0710440-1.2489393.

A small step for a man but a giant leap for mankind.Of course, requires 
a lot of testing to check whether this is /always/ the case.

All the best,
Helmut

-- 
Ing. Helmut Schütz
BEBAC – Consultancy Services for
Bioequivalence and Bioavailability Studies
W https://bebac.at/
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