[R-sig-ME] anova() and the difference between (x | y) and (1 | y:x) in lme4

Hans Ekbrand hans.ekbrand at gmail.com
Wed Jun 11 16:43:21 CEST 2014

On Wed, Jun 11, 2014 at 10:38:38AM -0400, Ben Bolker wrote:
>   Thanks Tierry.
>   I would add:
>   (1) for what it's worth, lme offers an intermediate model (compound
> symmetry), which allows for homogeneous but _negative_ within-group
> correlation ((1|var1:var2) only allows for non-negative within-group
> correlation)

OK, good to know for the future.

>   (2) the 'unstructured' (var1|var2) and 'grouped/positive compound
> symmetry' models (1|var1:var2) are in principle nested (all
> off-diagonals equal to zero, all diagonals identical -> simpler model),
> so you should be able to use a likelihood ratio test/ANOVA to test.

Great, thanks!

>   (3) your max|grad| convergence warnings are probably false positives;
> I would try scaling&centring your continuous predictors to see if that
> makes the eigenvalue warnings go away.

OK, will do. Thanks again!

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