[R] my error with augPred

[Petr Pikal]

Dear all

I try to refine my nlme models and with partial success. The model is 
refined and fitted (using Pinheiro/Bates book as a tutorial) but when 
I try to plot

plot(augPred(fit4))

I obtain
Error in predict.nlme(object, value[1:(nrow(value)/nL), , drop = 
FALSE],  : 
        Levels (0,3.5],(3.5,5],(5,7],(7,Inf] not allowed for 
vykon.fac
>

Is it due to the fact that I have unbalanced design with not all 
levels of vykon.fac present in all levels of other explanatory factor 
variable?

I try to repeat 8.19 fig which is OK until I try:

fit4 <- update(fit2, fixed = list(A+B~1,xmid~vykon.fac, scal~1),  
start = c(57, 100, 700, rep(0,3), 13))

I know I should provide an example but maybe somebody will be clever 
enough to point me to an explanation without it.

nlme version 3.1-75
SSfpl model
R 2.4.0dev (but is the same in 2.3.1), W2000.

Thank you
Best regards.

Petr PikalPetr Pikal
petr.pikal at precheza.cz