[Rd] mixed effects model and r-squared

Ben Bolker bolker at zoo.ufl.edu
Fri Dec 8 15:34:47 CET 2006

Indermaur Lukas <Lukas.Indermaur <at> eawag.ch> writes:

> Heya 
> I am fitting linear mixed effects model in R [snip]
> ts.model <- lme(LOG_FOC_MW ~ R_DN_SUM + ANIMAL + SEX+ YY, data = t.data,
random = ~ 1 | ANIMAL, 
> correlation=corCAR1(0.2, form = ~1 | ANIMAL ), 
method='ML', na.action=na.omit)). 
> Is there a possability to easly compute an R-square 
from the output of the
model summary?
> I would appreciate any hint.
> Best regards
> Lukas

  You probably need to repost this on r-help instead of r-devel;
it's not a "development" question.
   The other bad news for you is that I suspect it may be 
difficult to define r-squared uniquely for a mixed model.  
The resid() command  will give you
residuals, and you could take (1-resid()^2)/var(x) -- 
but how do you decide which var(x) to put in 
the denominator ... ?

  Ben Bolker

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