D Chaws <cat.dev.urandom <at> gmail.com> writes: > Say, for instance you want to model growth in pituitary distance as a > function of age in the Orthodont dataset. > > fm1 = lme(distance ~ I(age-8), random = ~ 1 + I(age-8) | Subject, data = > Orthodont) > > You notice that there is substantial variability in the intercepts (initial > distance) for people at 8 years, and that > this variability in initial distance is related to growth over time:
Looks like a perfect example to use parameter weight=varPower(something) in lme; you could use some power function of the initial distance. See Chapter 5.2 in Pinheiro-Bates. Dieter ______________________________________________ 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.
