[R] A question about nlmer in lme4 package

[Ben Bolker]

Patty Haaem via R-help <r-help <at> r-project.org> writes:


> Dear all,I have studied “Mixed models in R using the lme4 package
> Part 6: Nonlinear mixed models” by Douglas Bates. In this tutorial,
> there are some codes to fit nonlinear mixed models for Theoph
> data. The codes are as [follows:]

Th. start <- c(lKe = -2.5, lKa = 0.5 , lCl = -3)
nm1 <- nlmer ( conc ~ SSfol(Dose , Time ,lKe , lKa , lCl) ~
    0+ lKe+lKa+lCl +(0+ lKe| Subject )+(0+ lKa| Subject )+ 
    (0+ lCl| Subject ), nAGQ =0, Theoph , start = Th.start , verbose = TRUE )


>   I want to add a covariate (like age) to CL parameter. How should I
> modify above codes? what's more, how  are selected initial
> values (lKe = -2.5, lKa = 0.5 , lCl = -3) ?  Thanks in advanceElham

  You'll do better asking this question on r-sig-mixed-models at r-project.org
The short answer (to the first question) is that it's not easy, but it
can be done, see e.g.

http://stackoverflow.com/questions/15141952/nlmer-longitudinal-data
http://rpubs.com/bbolker/3423

  Ben Bolker