[R] Help with NLME

[Kent Holsinger]

I am relatively new to NLME, so the solution to the problem I describe here
may be obvious. But I've spent several days trying to get the right syntax
to formulate random effects for this model appropriately. The full model is:

  nlme(a ~ a.mitscherlich(a.qe, a.max, lcp, light),
       data=light,
       fixed = a.max + a.qe + lcp ~ trt,
       random = a.max + a.qe + lcp ~ 1 | bench/line,
       start = list(fixed=c(17.4305, 0.182444, 0.00928341, -0.00057221,
                            44.8384, 8.67678)),
       method="ML", verbose=T,
       control = nlmeControl(maxIter=250, msMaxIter=200, pnlsMaxIter=20,
                             gradHess=TRUE, returnObject=TRUE, niterEM=100))

What I'd like to do is to compare reduced models with something like

       random = list(a.max ~ 1 | bench, a.qe + lcp ~ 1 | bench/line)

i.e., to drop the nested term on each of the coefficients one by one so that
I can do and anova() to compare the models.

       random = a.max + a.qe +lcp ~ 1 | bench

works fine, but I can't figure out how to drop nested terms from only some
of the coefficients.

Any help (including pointers to appropriate pages in Pinheiro and Bates)
will be much appreciated.

Thanks.

Kent

--
Kent E. Holsinger                kent at darwin.eeb.uconn.edu
                                 http://darwin.eeb.uconn.edu
-- Department of Ecology & Evolutionary Biology
-- University of Connecticut, U-3043
-- Storrs, CT   06269-3043