Gary Dong <pdxgary163 <at> gmail.com> writes: > I'm estimating a two-level regresion model but having difficuly in finding > a good R syntax example. > > Let me use an example to explain what I'm doing. The dependent variable is > math score (mathscore). Predictors are at two levels. At the student level, > they are household income (hinc) and IQ (IQ). At the school level, there is > a dummy variable indicating if the school is a private school (prvsch). I > also have school IDs (id) that can be used as the subject. > > I'm wondering what the syntax would be in R. Any advice is appreciated.
When using lme4 you don't need to explicitly state which fixed-effect predictors are at which level; the simplest model would use mathscore ~ hinc + IQ + prvsch + (1|id) You might want to consider whether the effects of household income and IQ vary by school or not: mathscore ~ hinc + IQ + prvsch + (hinc+IQ|id) (the intercept is implicit in all cases, this would be the same as using (1+hinc+IQ|id)) The full 3x3 covariance matrix is estimated in this case; if you want to force independent variation of intercept, hinc, IQ within schools, use mathscore ~ hinc + IQ + prvsch + (1|id) + (0+hinc|id) + (0+IQ|id) Further questions on mixed models in R should probably go to r-sig-mixed-mod...@r-project.org ______________________________________________ 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.
