[R] nls - can't get published AICc and parameters

Roland Sookias r.sookias at gmail.com
Tue Jul 26 23:20:21 CEST 2011


I'm trying to replicate Smith et al.'s
(http://www.sciencemag.org/content/330/6008/1216.abstract) findings by
fitting their Gompertz and logistic models to their data (given in
their supplement). I'm doing this as I want to then apply the
equations to my own data.

Try as a might, I can't quite replicate them. Any thoughts why are
much appreciated. I've tried contacting the authors but I think
they're away.

The equations as I've used them are:




The data file I've been using is attached. It starts at the K-Pg
boundary with a body size of 3.3kg, following their description in the

Their parameters and AICc values are given in their paper. I get
something quite close for some of them (~0.245 G, their gamma, K
estimates reasonable etc.), but in the logistic model C is more like 3
than 1.5, and the AICc values differ by ~10 rather than ~1.



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