jerome@hivnet.ubc.ca
2003-Apr-01 21:23 UTC
[Rd] lme() and nlme() give inconsistent numbers of degrees of freedom (PR#2384)
I apologize for cross-posting. In the reproducable example below, I fit the same model with lme() and nlme(). However, I get 12 degrees of freedom with lme() and 2 df with nlme(). library(nlme) set.seed(14) a <- 2 x <- rep(rnorm(3),rep(5,3)) id <- rep(c("a","b","c"),rep(5,3)) y <- a+x+rnorm(15) data <- data.frame(y=y,id=id) initx <- matrix(x[c(1,6,11)],dimnames=list(c("a","b","c"),"x")) summary(fit.lme <- lme(y ~ 1,data=data,random=~1|id,method="ML")) summary(fit.nlme <- nlme(y ~ a + x, fixed= a~1, random=x~1|id, data=data, start=list(fixed=c(a=2), random=list(id=initx)),method="ML")) When I try the same thing with set.seed(18), I get 12 df for both. I have submitted a bug report on that issue on Dec 20th and I have tried to find the source of the problem, but no success. You can check what I found so far at: http://r-bugs.biostat.ku.dk/cgi-bin/R/Add-ons?id=2384 Can anyone help find the source of this problem? Sincerely, Jerome Asselin R 1.6.2 on Red Hat Linux 7.2 Package: nlme 3.1-38