Dear all,

We are trying to do a meta regression in R using the lme function. The 
reason for doing this with lme function is that we have covariates and 
studies within references. In S-Plus this is possible by using the 
following command:

lme(outcome ~ covars, random = ~1 | reference/study, weights = 
varFixed(~var.outcome), data = mydata, control = lmeControl(sigma = 1))

This means that the residual variance is equal to var.outcome times sigma, 
where sigma is fixed to 1.

In R we do not know how to fix sigma = 1 in the lmeControl. Has anyone 
experience with this? If so, how can we solve this problem?

We can't stand that we can do it in S-Plus, but not in R!

Jan van de Kassteele
Maarten Schipper



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