On Mon, Feb 21, 2011 at 10:06 PM, dadrivr <dadr...@gmail.com> wrote: > > Thanks Dennis, > > The code works for perfectly for the data in the example. For some reason, > however, I get the following error message when I use a different data set: > >> preds <- expand.grid(age = c(30,36,42), Subject = unique(mydata$id)) >> predict(lmemodel, preds, na.action=na.omit) > > Error in predict.lme(lmemodel, preds, na.action = na.omit) : > Cannot evaluate groups for desired levels on "newdata" > > I searched for the error online, and it appears that it results from missing > subject IDs (see: > http://www.mail-archive.com/r-help@r-project.org/msg100649.html). I checked > both the newdata file ('preds') and the predicted values of lmemodel > ('predict(lmemodel)'), however, and the subject IDs appear to be in both > files. I'm not sure if it's an issue, but the length of the predicted > values is shorter (with fewer IDs) than the newdata file (preds) because > there is missing data. Any help would be greatly appreciated on this.
Check str(preds) to make sure that Subject is a factor in the output of expand.grid. It is possible that expand.grid converts to another storage mode. > If it is diagnostic, I attached a .txt file to this message with the > contents of preds and predict(lmemodel): > http://r.789695.n4.nabble.com/file/n3318524/lmemodel.txt lmemodel.txt > -- > View this message in context: > http://r.789695.n4.nabble.com/Plotting-individual-trajectories-from-individual-growth-model-tp3315494p3318524.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. > ______________________________________________ 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.
