[Help-gsl] Multidimensional least-square-fit sought

[Matthias Sitte]

Hi,

I'm looking for a way to to a least-square-fit to a data set (x,y,z). 
The fit function should be a polynomal like the following:

  z(x,y) = \sum_{m,n=0,m+n<=N}^{N} c_{mn} x^m y^n
         = c_{00} + c_{10} x + c_{01} y
           + c_{20} x^2 + c_{11} xy + c_{02} y^2 + ...

I've been using GSL a lot and know my way around, but I don't know the 
terminology of least-square-fits, so I'm kindly asking you to name the 
proper function(s) I should use before I lose myself in the docs ;-)

Thx,
  Matthias