[R] Help Derivate for Nonlinear Growth Models

Ben Bolker bbolker at gmail.com
Wed Jan 26 15:13:13 CET 2011

acocac <acocac <at> gmail.com> writes:

> Hi!! Im doing my graduated work in Onion Curves Growth with Nonlinear Models,
> I'm amateur in R so i have  doubt how i put or program next models,
> http://r.789695.n4.nabble.com/file/n3236748/96629508.png 
> Also, i cant derivate for Gauss Model, and Richard Model dont have funtion,
> If someone could help me, i was so grate,

  You need more help than we can give you here ... You need to 
use the ?nls function. I think if you are going to be doing a serious
project fitting nonlinear growth models, you should probably learn or
refresh enough calculus so that you can compute the derivatives yourself
(R can do some small bit of analytic differentiation -- see ?D -- but
it doesn't simplify at all, so the answers are quite often uglier than
if you did the computation by hand). 
  You don't absolutely need the derivative to use nls(), although it
helps a lot.

  I would also suggest going to Google scholar and
searching for 'nls "growth curve" Bates" to find some papers that
have used this approach.

  If you need to post again, please read the posting guide and
show us how far you have managed to get on your own.

  good luck,
   Ben Bolker

More information about the R-help mailing list