Hello, I am trying to run a multilevel probit model using Zelig, but keep receiving the following error message: " in .deparseTag(TT.vars[[vind]]) : wrong use of tag function!!" A simplified version of the model I am trying to run is: z.out <- zelig(formula= list(mu=investment.binary ~ edlevel + tag(1 + edlevel, gamma | country), gamma = ~ tag(GDPpc06.full| country)), data=data2006.mod1, model="probit.mixed") What I would like to do is allow the intercept and the edlevel variable listed within the first tag() to vary by country as a function of the GDPpc06.full variable, all of which are included in the same dataframe. I followed the syntax here - http://cran.r-project.org/web/packages/Zelig /vignettes/probit.mixed.pdf - but I think that I am incorrectly specifying the gamma part of the syntax, which may be causing the error. I *am* able to get the model to run when I allow the intercept and edlevel variable to vary using the following syntax: z.out <- zelig(investment.binary ~ edlevel + + tag(1 + edlevel | country), data=data2006.mod1, model="probit.mixed") However, this syntax does not allow me to specify that the intercept and edlevel variable should vary as a function of GDPpc06.full, as in the first model specified above. I have tried including multiple tags at the non-group level of the model specification - i.e. one for the intercept and one for the edlevel variable - but this does not seem to work either. Do you have any suggestions for how to fix the syntax? Sincerely, Jason -- Jason I. McMann PhD Student | Department of Politics Princeton University | jmcmann(a)princeton.edu