Have you considered 'simulate.lme'? I believe that this is what
Bates included in the 'nlme' package for obtaining confidence intervals,
joint confidence regions, etc., when there were questions about the
results for whatever reason. I have not tried it with a singular model,
but I
1, 2006 9:31 AM
> To: r-help@stat.math.ethz.ch
> Subject: [R] non positive-definite G matrix in mixed models:
> bootstrap?
>
> Dear list,
> In a mixed model I selected I find a non positive definite
> random effects variance-covariance matrix G, where some
> parameters a
Dear list,
In a mixed model I selected I find a non positive definite random effects
variance-covariance matrix G, where some parameters are estimated close to
zero, and related confidence intervals are incredibly large.
Since simplification of the random portion is not an option, for both
inte
