Cudeck & du Toit (2002) model in R

Anyone ever tried to do the Cudeck & duToit (2002) reparameterized quadratic growth model in R?

are you requesting specific help, or conducting a survey?

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can you provide the paper?
is the data you want to run it on public or private? (if public, would you share it so forum members can try to work on it ?)

I am hoping to understand how to do the model in R. I have not been able to find syntax and am not skilled enough to write the code myself.

The three parameters in the model are described in the paper. Parameters correspond to initial point, maximum value, and 'maximizer' (i.e., how long it took the subject to reach their peak value).

I suspect it would involve the nlme package.

I tried to upload it here but new users are not allowed to upload documents. Please try this link:

The data are private but I will create a modified version for this and provide it soon. Thank you!