[R] Non-linear random variables

[Han Lai]

Hi, Norm

Although I have not done it for Ricker's SR curves, I did logistic curves (for
selectivity) and von Bertalanffy growth curves.  You can find the examples in the
book

Pinherio, J.C., and Bates, D.M.  2000.  Mixed-effects models in S and S-Plus.
Springer, N.Y.

The sec. 8.2, p.354 (actually p.356), there is an example on growth of orange trees
I believe that you can modify the program there.  I use the similar approach for my
work.  It works sometimes but not always.  Convergence is a major problem because
our fisheries data are often very noise.  Be careful to check you have enough
degrees of freedom to fit the model.  Let me know if you have other questions.

Good Luck!

Cheers!
Han-Lin Lai, Ph.D
Northeast Fisheries Science Center
Woods Hole, MA 02543
Han-Lin.Lai at noaa.gov
508-495-2312


"Good, Norman" wrote:

> I have a fisheries Ricker stock-recruitment non-linear model which I am
> trying to code up in R (after failing in MATLAB). There are two fixed
> parameters and a random environmental effect that is linked to a first order
> lagged correlation fixed parameter.
>
> Are there any examples of fitting this model I could follow?
>
> Cheers
>
> Norm Good
>
> Fisheries Biologist (Mathematician)
> Southern Fisheries Centre
> PO Box 76, Deception Bay Q 4508
> telephone 3817 9588, fascimile 3817 9555
>
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