[R] lmm WITHOUT random factor (lme4)

[Mark Difford]

On Mar 17, 2011; 11:43am Baugh wrote:

>> Question: can I simply substitute a dummy var (e.g. populated by zeros)
>> for "ID" to run the model 
>> without the random factor? when I try this R returns values that seem
>> reasonable, but I want to be sure 
>> this is appropriate.

If you can fit the model using lme (and it looks like you easily can) then
another check would be:

## Compare models with and without random effects
fm <- lm(Reaction ~ Days, sleepstudy)
fm1 <- lme(Reaction ~ Days, random= ~1|Subject, sleepstudy)
anova(fm1, fm)                 ## lme-fitted model must come first

Regards, Mark.

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