[Help-gsl] Re: non-linear least squares fitting

[Richard Henwood]

Jay Howard wrote:

> Thanks for the help, Barrett.  My responses follow yours:
> 
>> Typical usage would be to use gsl_multifit_fdfsolver_lmsder or
>> gsl_multifit_fdfsolver_lmsder as the gsl_multifit_fsolver_type. Look at
>> the variable "T" in the example here:
>> http://www.gnu.org/software/gsl/manual/html_node/Example-programs-for-Nonlinear-Least_002dSquares-Fitting.html
> 
> I was hoping to avoid using the fdfsolver set of calls because they
> require that I furnish df() and fdf() functions, which I'm not clear
> on how to implement based on f().  

<snip> 

Hi folks, 

Since you are on this topic I thought I would introduce my experience;
fitting a log-normal distribution (f) with two degrees of freedom to data.

I implement fdf using numerical partial differentiation of f. 

This method (numerical partial differentials) appeared to work; 
is this a reasonable approach?

or am I missing something;

thanks for your thoughts;
r