>>>>> "Rick" == Rick Bilonick <[EMAIL PROTECTED]> >>>>> on Wed, 30 Nov 2005 23:11:07 -0500 writes:
Rick> I'm trying to fit a generalized mixed effects model to a data set where Rick> each subject has paired categorical responses y (so I'm trying to use a Rick> binomial logit link). There are about 183 observations and one Rick> explanatory factor x. I'm trying to fit something like: Rick> (lmer(y~x+(1|subject))) If you want binomial you have to give ' family = binomial ' to lmer ! Further, always using 'data = ..' is generally recommended practice, and I'd rather assign the result of lmer(.) than just print it, i.e. (if you want to print too): (model1 <- lmer(y ~ x + (1|subject), data = <your DFrame>, family = binomial)) and in your case y should be the 2-column matrix cbind(successes, failures) Martin Maechler, ETH Zurich Rick> I also tried fitting the same type of model using glmmPQL from MASS. In Rick> both cases, I get a t-statistic that is huge (in the thousands) and a Rick> tiny p-value. (Just for comparison, if I use lrm ignoring the clustering Rick> I get a t-statistic around 3 or so and what appears to be a reasonable Rick> estimated coefficient which is very close to the estimated coefficient Rick> using just one observation from each subject. Rick> Most of the subjects have two responses and in almost all cases the Rick> responses are identical although the explantory factor values are not Rick> always identical for each subject. Rick> If I use geeglm from geepack, I get reasonable estimates close to the Rick> naive model results. Rick> I also tried using the SAS glimmix macro to fit a generalized mixed Rick> model and the routine does not converge. Rick> Why does geeglm appear to work but not lmer and glmmPQL? Is this likely Rick> to be due to my particular data set? Rick> Rick B. Rick> ______________________________________________ Rick> R-help@stat.math.ethz.ch mailing list Rick> https://stat.ethz.ch/mailman/listinfo/r-help Rick> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html