Karl, Apologies for the delay, but we are just now getting to the ZeligMultilevel module. I fixed the issue that you raised, and your code example now runs using the current Beta versions of Zelig and ZeligMultilevel. To install these, install the packages as follows: install.packages("Zelig", type = "source", repos = "http://r.iq.harvard.edu/") install.packages("ZeligMultilevel", type = "source", repos = "http://r.iq.harvard.edu/") Best, James -- James Honaker, Senior Research Scientist //// Institute for Quantitative Social Science, Harvard University ________________________________ From: zelig-bounces(a)lists.gking.harvard.edu [zelig-bounces(a)lists.gking.harvard.edu] on behalf of Karl Kosciuch [kosciuch(a)gmail.com] Sent: Thursday, March 21, 2013 10:48 PM To: zelig(a)lists.gking.harvard.edu Subject: [zelig] assistance with predictions for logit.mixed Hello - I was happy to find the Zelig package as I had been looking for code for implementing a generalized linear mixed model. I'm having some issues obtaining predicted probabilities from my rather simple logit.mixed regression. I am using logit.mixed with avoidance behavior as the binomial response variable, height as the predictor (ranging from 150 to 1500m), and year as a random effect (there are 3 years). The model runs fine, but I encounter an error starting with x.out. I've looked at the package documentation to try to solve the error, and have been unsuccessful. I'd like to produce one figure showing with the predicted probability on the y-axis and height on the x-axis. I'd like to show the regression line with the 95% CI for the predicted probabilities. I've been successful at coding this analysis and figure for a fixed effects logistic regression, but not so much for the mixed effects logistic regression. Thank you library(Zelig) library(ZeligMultilevel) avd$year <- factor(avd$year) z.out <- zelig(avoid ~ height + tag(1|year), data = avd, model = "logit.mixed") summary(z.out) x.out <-setx(z.out, fn = NULL) s.out <- sim(z.out, x = x.out) summary(s.out) Error in array(x, c(length(x), 1L), if (!is.null(names(x))) list(names(x), : 'data' must be of a vector type Error in summary(s.out) : error in evaluating the argument 'object' in selecting a method for function 'summary': Error: object 's.out' not found -- Karl Kosciuch kosciuch@gmail.com<mailto:kosciuch@gmail.com>