[R] Help - Curvature measures of nonlinearity

Ravi Varadhan rvaradha at jhsph.edu
Mon Jun 2 16:43:07 CEST 2003


How about "rms.curv" function in the MASS library?

Ravi.

----- Original Message -----
From: Ivone Figueiredo <ivonefig at ipimar.pt>
Date: Monday, June 2, 2003 4:40 am
Subject: [R] Help - Curvature measures of nonlinearity

> Dear colleagues,
> 
> Von Bertalanffy model is commonly adjust to data on fish length 
> (TL) and age (AGE) 
> TL= Linf*(1-exp(-K*(AGE-t0)). Linf, K and t0 are parameters of the 
> model.One main goal of the growth study is the comparison of 
> growth parameter estimates between sexes of the same species, or 
> estimates from different populations. 
> The realibility statistical tests normally applied are highly 
> dependent on the nonlinearity of the model used.
> 
> Are there any developed routines in R ? to:
> 1) calculate the maximum intrinsic curvature
> 2) maximum parameter affecting curvature 
> 3) plot the two dimensional cross sections of confidence regions 
> (for different alpha values) of the model parameters
> 
> Regards,
> Ivone Figueiredo 
> 	[[alternate HTML version deleted]]
> 
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