Hello Jan, As far as know, fixing sigma to 1 is not possible in R with lme. That is why I started to write my own functions to allow me to fit mixed-effects models in R. Quite some time ago, I put one of those functions on my website, which can be downloaded here: http://www.wvbauer.com/downloads.html. Since some people have indicated to me that they have found the function useful, I have been expanding the function into a full package, which I will be relasing shortly. It includes a much-improved version of the function that is currently on my website and methods for printing, ploting, residual extraction, influence diagnostics, and so on. The Mantel-Haenszel and Peto's method are also implemented. In a second stage, I will be adding functions to fit the bivariate mixed-effects model and then a multivariate model function, which is useful for more complex syntheses (such as when doing a meta-analysis of mixed-treatment comparisons). So maybe the upcoming package will be useful to you.
Best, -- Wolfgang Viechtbauer Department of Methodology and Statistics University of Maastricht, The Netherlands http://www.wvbauer.com/ ----Original Message---- From: r-help-boun...@r-project.org [mailto:r-help-boun...@r-project.org] On Behalf Of Jan van de Kassteele Sent: Wednesday, April 29, 2009 15:02 To: r-help@r-project.org Subject: [R] meta regression in R using lme function > 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 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.