I am using lmList, which takes 'Data' partitioned according to the levels of a grouping factor (gf) and individual 'lm' fits are obtained for each 'data'partition, using a model defined as in "lm". So my call to lmList looks something like:
> mg.lis <- lmList(strmbf ~ age1c + gender1 + sysbp.clinic + + diabp.clinic + ldl1 + mets.total + bmi1c | gf, + data = Data, subset= avblock=="normal"); but I get a strange error message: "Error in model.frame.default(formula = form, data = dat, na.action = na.action, : object is not a matrix" If I remove either mets.total or bmi1c from my model, then the routine works fine, i.e. it works when either of the two variables are in the model, but not when I add one both variables to the model. Similarly I can remove any other variable and put both mets.total and bmi1c back into the model, and it works. It seems like the number of model variables can not exceed 7 for some reason I fail to understand. I have 1809 cases and the gf factor subdivides this into 3 about equally sized groups. Therefore the model could have much more than 8 degrees of freedom. Also I removed all cases from the dataframe with "NA", so NA's can not explain the problem either. Any suggestions of what could have gone wrong? As further information I also add that I used "lme" in the same "nlme" package to perform multi-level regression modeling (linear mixed effects) and do not have any similar problems. Also I can "manually" perform the analysis with "lm" for the data subsets corresponding to each of the 3 levels of the grouping factor (gf is the grouping variable), without any problem. thanks in advance for help! Michael Jerosch-Herold ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
