R help - Jul 2015 - A question about nlmer in lme4 package

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 fallows:?>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
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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