[R-sig-ME] algal nonlinear mixed effects problem

[Ben Bolker]

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  Inspired by a recent question of Diego Pujoni's on the list
( http://article.gmane.org/gmane.comp.lang.r.lme4.devel/9363/match= ),
I started working on the problem, with two realizations:

 1. the problem really needs a nonlinear fit: see
http://rpubs.com/bbolker/3363

 2.  I have no idea how to do an nlmer fit with a non-trivial
fixed-effects model (e.g. in nlme we could do

nlmefit1 <- nlme(model = X ~ SSfpl(Day, asymp.L, asymp.R,
                                   xmid, scale),
   fixed = list(asymp.R ~ Group, xmid + scale + asymp.L ~ 1),
   random = asymp.R ~ 1 | Individual, ...)

  This was raised earlier on stack overflow:

http://stackoverflow.com/questions/11056625/how-to-add-fixed-effect-to-four-parameter-logistic-model-in-nlmer

  has anyone figured out if this is possible/how to do it ?

  Ben Bolker
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