Thanks Joshua for the clear explanation. I've previously posted in r sig mixed, but I got no response... :(
Cheers, - Camila On Mon, Jul 2, 2012 at 9:31 PM, Joshua Wiley <jwiley.ps...@gmail.com> wrote: > Hi Camila, > > In mixed equation form instead of multilevel, it would be: > > Y_it = gamma_00 + gamma_10*X_it + gamma_11*W_it*X + (e_it + u_0t + u_1j*X) > > your code seems reasonable. Note that the random intercept and slope > will be correlated in your specification (unstructured if you want, it > is possible to force out, but is sensible starting place) > > model <- lmer(Y ~ X + X:W + (X | ID), data = data) > > which gives: > residual variance: e_it > variance of intercept (constant term, gamma_00): u_0t > variance of slope (gamma_10): u_1j*X > > as well as overall estimates for the intercept, slope of X, and the > interaction of X and W. > > Bert is correct that R sig mixed models is the more appropriate list, > but many people read both and there is no reason it cannot be answered > here. > > Cheers, > > Josh > > > On Mon, Jul 2, 2012 at 6:47 PM, Camila Mendes <cacamende...@gmail.com> > wrote: > > Hey all - > > > > I am a newbie on mixed-effects models. I want to estimate the following > > model: > > > > Y_it = alpha_0t + alpha_1t*X_it + e_it > > alpha_0t = gamma_00 + u_0t > > alpha_1t = gamma_10 + gamma_11*W_it + u_1j > > > > Where Y is my outcome, X is my level-1 predictor, and W is my level 2 > > predictor. > > > > I am not sure if I am doing it right. Is this the correct specification > of > > the formula? > > > > model = lmer(Y ~ X + X:Y + ( X | ID), data = data) > > > > Also, can you help me to write down the combined model formula? I tried > > by substituting on the first equation, but I got some weird interactions > > with the residual (?) > > > > Thanks a lot! > > > > - Camila > > > > [[alternative HTML version deleted]] > > > > ______________________________________________ > > 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. > > > > -- > Joshua Wiley > Ph.D. Student, Health Psychology > Programmer Analyst II, Statistical Consulting Group > University of California, Los Angeles > https://joshuawiley.com/ > [[alternative HTML version deleted]] ______________________________________________ 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.
