[Help-gsl] Bspline fitting

[Caterina Michelagnoli]

Hi,

I would like to make a cubic spline fit to 
experimental data and I am trying to employ 
gsl tools for this scope, starting from the
example given at the end of the chapter on
Basis Splines of the User Guide. What I did
not understand is the difference between knots
and breakpoints. From a more "practical" point
of view: what shall I do if I want to divide
the x axis in --for example-- 3 regions, in
which the experimental data have to be fitted
by 3rd order polynomials, and let the x positions
of the border points of these regions being 
introduced by the user?

Thanks
CM