[R-sig-ME] Trouble Replicating Unstructured Mixed Procedure in R

[David Duffy]

On Tue, 24 Jan 2012, Charles Determan Jr wrote:

> Greetings,
>
> I have been working on R for some time now and I have begun the endeavor of
> trying to replicate some SAS code in R.  I have scoured the forums but
>
This is also the Orthodont dataset, distributed with nlme.

As David Atkins pointed out, R defaults to Type I SS. so you would need to 
use, for example, the Anova() command from the car package.  The other 
thing is that the SAS F statistics are only approximate, depending on 
which covariance structure is chosen (perhaps John Maindonald or someone 
clever could comment), so SAS offers different possibilities for ddf eg

http://www2.sas.com/proceedings/sugi26/p262-26.pdf

while lme and lmer offer one or none.

-- 
| David Duffy (MBBS PhD)                                         ,-_|\
| email: davidD at qimr.edu.au  ph: INT+61+7+3362-0217 fax: -0101  /     *
| Epidemiology Unit, Queensland Institute of Medical Research   \_,-._/
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