I am making a little GUI for lme4, and I was wondering if there is a function that automatically detects on which level every variable exists. Furtheremore I got kind of confused about what a random effects model actually calculates.
I have some experience with commercial software packages for multilevel analysis, like HLM6, and I was surprised that lme4 does not require the user to specify the level for every predictor variable. Is this because the function automatically detects the level by testing on which levels the predictor has variance, or is this information simply not needed? I was taught that a crosslevel interaction predicts the regression coefficient of the lower level variable, which is also what is implied by the HLM gui. However, in an lme4 formula, a crosslevel interaction has the same syntax as a regular interaction term. Furthermore, lme4 also allows adding crosslevel interactions without a random slope for the lower level variable. Now I'm confused. Is there a fundamental difference between a crosslevel interaction, or is the same thing as a regular interaction when the model also holds an error term for the lower level variable? ----- Jeroen Ooms * Dept. of Methodology and Statistics * Utrecht University Visit http://www.jeroenooms.com www.jeroenooms.com to explore some of my current projects. -- View this message in context: http://www.nabble.com/lme4-and-Variable-level-detection-tp22262944p22262944.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.