[R] Question on nlme

[Eric Berger]

Just reading the documentation, it seems the argument
'lmeControl(opt="optim")' says to use the optim optimizer.
Then the R command ?optim describes what is done.

?optim

    "General-purpose optimization based on Nelder-Mead, quasi-Newton
     and conjugate-gradient algorithms. It includes an option for
     box-constrained optimization and simulated annealing."



On Sat, Sep 20, 2025 at 10:55 AM sasha a <watermelon_canada using outlook.com>
wrote:

> Hello,
>
> I am using the nlme package in R:
>
> model <- lme(
>     response ~ response_type + x_y + x_z - 1,
>     random = ~ response_type - 1 | group,
>     weights = varIdent(form = ~ 1 | response_type),
>     data = data_long,
>     control = lmeControl(opt = "optim")
> )
>
> Is it possible to know what estimation process this is using? For example,
> is it using EM? Or is it use Newton-Raphson with GLS/RMLE?
>
> Thanks!
>
>
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