[R] nested ANOVA using lme

[David Semmens]

I have an ANOVA model with 2 factors "Environment" and "Site", 
"Diameter" is the response variable. Site should be nested within 
Environment. Site is also a random factor while Environment is fixed. I 
can do this analysis using the "aov" function by using these commands:

 >model<-aov(Diam~Env+Error(Env%in%Site),data=environ)
 >summary(model)
 >summary(aov(Diam~Env/Site,data=environ))

But the model is unbalanced and I want to calculate estimates of the 
variance components. In this case the REML approach should give more 
reliable estimates than the method I have used. But I am unable to work 
out how to specify a nested factor using the "lme" function. I have 
tried:

 >firstgo<-lme(Diam~Env+Env:Site,data=environ)
 >secondgo<-lme(Diam~Env+Env%in%Site,data=environ)
 >thirdgo<-lme(Diam~Env+Env/Site,data=environ)

But I keep getting this error:

Error in getGroups.data.frame(dataMix, groups) :
	Invalid formula for groups

If anyone could help me with code for specifying a random nested factor 
using lme that would be great.

Thanks,
David Semmens.