Hi everone, I have a question on using lme on a mixed effects model.
The linear mixed model is in the form of: y = bX +Zu + e where "X" and "Z" are the matrices, "b" is the coefficient vector of fixed effects, "u" is the coefficient vector of random effects, and e is an error vector. I would like to use "lme" function to fit the model and estimate "b" and "u". However, there is an error when I call the lme function: fit = lme(y ~ int + X1 + X2 + X3, data = data.fr, random = ~ Z1 + Z2 + Z3 + Z4 + Z5) where: int is a vector of 1 in matrix X, used for the intercept term "b0", X1, X2, X3 are columns of matrix X, Z1 to Z5 are columns of matrix Z, data.fr = data.frame(y,X,Z). I got the error message: Error in getGroups.data.frame(dataMix, groups) : Invalid formula for groups Could you please suggest me know to solve this problem? Do I use incorrect arguments? Thank you very much. Nantachai ______________________________________________ R-help@stat.math.ethz.ch 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.