Re: [Help-gsl] Nonlinear fitting

[jeremy theler]

Ken,

If you just need a quick answer to your problem, I would like you to try my 
tool called wasora, which amongst other things, is a high-level interface to 
some of the GSL tools.

I have added your fitting problem to the examples subdirectory (I made up the 
data). You can take a look at it by first downloading the tarball from

http://www.talador.com.ar/jeremy/wasora/

and the looking at examples/fit.was

Sadly, the code is lacking good documentation. So far all I have are examples 
of usage. In the following link

http://www.talador.com.ar/jeremy/wasora/realbook/._realbook015.html

some comparison between GSL examples written in C as taken from the manual and 
the (almost) the same results obtained with wasora by using a far more simple 
high-level input file.

Regarding your fitting problem, wasora takes care of numerically computing the 
gradient of the function with respect to the parameters if explicit algebraic 
expressions are not given.



--
jeremy

On Thursday 03 July 2014 18:07:40 address@hidden wrote:
> Hi,
> I am trying to fit the nonlinear equation:
> P = C0 + C1*X + C2*X^r
> where C0, C1, C2 and r are variables to be fitted, P and X are vectors
> of known observations.
> I have read the docs and I'm trying to modify the example program. I'm
> struggling to provide the expb_f, expb_df, expb_fdf functions.
> I would like advice on how to proceed.
> Regards,
> Ken