[R] nlme Indometh SSbiexp

[Boldi]

Dear all,
Probably a very stupid question.
I am trying to reproduce the example of Pinheiro & Bates pp.278--287 on 
R 3.0.2 (Windows).

I'd like to run :

###
mod.nls <- nls(conc ~ SSbiexp(time, A1, lrc1, A2, lrc2), data=Indometh)
mod.lis <- nlsList(conc ~ SSbiexp(time, A1, lrc1, A2, lrc2), data=Indometh)

mod1 <- nlme(model=mod.lis, data=Indometh,
              random = pdDiag(A1 + lrc1 + A2 + lrc2 ~ 1))

>mod1
Nonlinear mixed-effects model fit by maximum likelihood
   Model: conc ~ SSbiexp(time, A1, lrc1, A2, lrc2)
   Data: Indometh
   Log-likelihood: 54.59671
   Fixed: list(A1 ~ 1, lrc1 ~ 1, A2 ~ 1, lrc2 ~ 1)
         A1       lrc1         A2       lrc2
  2.8275372  0.7736221  0.4614716 -1.3441022

Random effects:
  Formula: list(A1 ~ 1, lrc1 ~ 1, A2 ~ 1, lrc2 ~ 1)
  Level: Subject
  Structure: Diagonal
                A1      lrc1        A2       lrc2   Residual
StdDev: 0.5714106 0.1580778 0.1115978 7.3195e-06 0.08149341

Number of Observations: 66
Number of Groups: 6


###

which works well. But I'd like to directly specify the model with nlme, 
not going through "nls" or "nlsList" (please don't ask why...). Below 
the result. I don't get what I am missing?

###

>mod2 <- nlme(model=conc ~ SSbiexp(time, A1, lrc1, A2, lrc2), data=Indometh,
+fixed = A1+lrc1+A2+lrc2~1,
+random = pdDiag(A1 + lrc1 + A2 + lrc2 ~ 1))
Error in nlme.formula(model = conc ~ SSbiexp(time, A1, lrc1, A2, lrc2),  :
   subscript out of bounds

###




	[[alternative HTML version deleted]]