[R] [R-pkgs] New version of lme4 and new mailing list R-SIG-mixed-models

From: Douglas Bates <bates_at_stat.wisc.edu>
Date: Thu 25 Jan 2007 - 23:12:00 GMT

Version 0.9975-11 of the lme4 package has been uploaded to CRAN. The source package should be available on the mirrors in a day or two and binary packages should follow soon after.

There are several changes in this release of the package. The most important is the availability of a development version of lmer called, for the time being, lmer2. At present lmer2 only fits linear mixed models. Generalized linear mixed models will be added "soon". Furthermore there is no mcmcsamp method for a model fit by lmer2. This deficiency will also be rectified "soon". Once I have all the capabilities and methods currently available for lmer also available for the new representation I will remove the old representation and rename lmer2 as lmer.

The current version of lmer will continue to be available throughout the migration process. You don't have to change anything about your use of that function unless you want to try the new one. It would be a good idea, however, to save the data and the call to lmer in addition to saving an lmer object, if you so choose, so that you can recreate the fitted model when the development version becomes the release version.

The package contains a vignette giving the details of the new implementation.

The reason I am releasing a development version in parallel with the production version is because I would like feedback from useR's regarding the development version. In my experience, testing it myself and with colleagues whom I visited recently, I have found that lmer2 is faster and more reliable than the current lmer. In particular, on some difficult model fits I have been able to get substantially better parameter estimates (i.e. the deviance at the lmer2 estimates is perhaps 4 or 5 lower than that at the lmer estimates) with lmer2 than I could with lmer.

If you have fit a linear mixed model using lmer and are willing to try it with lmer2 I would appreciate your telling me if the parameter estimates are comparable and which fit was faster (use system.time() to check). I'm primarily interested in models fit to large data sets or "difficult" fits.

We have established a new mailing list, R-SIG-mixed-models, for discussion of R software to fit mixed-effects models, especially lmer.  See https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models for information or to subscribe.

I know that I have said this before but this is the last time that I am going to change the underlying representation. Really - trust me - this is the last time. My theory of software development is expressed in a line from an old blues song, "you just keep doing it wrong till you do it right". I'm convinced that this time I have it right. That statement sounds like "famous last words", doesn't it? :-)

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