[R] anova applied to a lme object

[Berta]

Hi R-users,

when carrying out a multiple regression, say lm(y~x1+x2), we can use an 
anova of the regression with summary.aov(lm(y~x1+x2)), and afterwards 
evaluate the relative contribution of each variable using the global Sum of 
Sq of the regression and the Sum of Sq of the simple regression y~x1.

Now I would like to incorporate a random effect in the model, as some data 
correspond to the same region and others not:  mylme<- lme(y~x1+x2, random= 
~1|as.factor(region)). I would like to know, if possible, which is the 
contribution of each variable to the global variability. Using anova(mylme) 
produce an anova table (without the Sum of Sq column), but I am not sure how 
can I derive the contribution of each variable from it, or even whether it 
is nonsense to try, nor can I derive a measure of how much variability is 
left unexplained.

Sorry for the type of question, but I did not find a simple solution and 
some researchers I work with love to have relative contributions to global 
variability.

Thanks a lot in advance,

Berta



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