In gsl help is written (section 38.4): " For the algorithms which require a Jacobian matrix of derivatives of the fit functions, there are times when an analytic Jacobian may be unavailable or too expensive to compute.
Therefore GSL supports approximating the Jacobian numerically using finite differences of the fit functions. " Does somebody implemented above method of nonlinear fitting ? Short information in gsl help says: "This is typically done by setting the relevant function pointers of the gsl_multifit_function_fdf data type to NULL" but code based on these method doesn't work. Program finishes with segmantation fault. If somebody knows the answer and can put example code I will be grateful [email protected] Kaz
