In the non-linear least squares fitting, is there no way to hold a parameter fixed? My strategy has been to declare a global array of parameters and flags. If in the gsl_multifit_function_fdf evaluation, the fix flag is found to be set, then use the global (original) parameter value, instead of the one supplied by the fdfsolver.
The problem with this is the fdfsolver continues to change the parameter, but can't know that the returned values (f and J) were evaluated using the fixed parameter. Does this send the fdfsolver on a wild chase, and is the chi-squared or covariant matrix wrong in the end? Has anyone else found a way around this problem? PS. The manual text on the non-linear least squares fitting follows from the section on multidimensional minimization. But in this case, I find the notion of parameters and x values to be backwards. Most would expect "x" to be the name of the data point, and not the parameter to be minimized. -------------------------------------- [EMAIL PROTECTED] Canadian Neutron Beam Centre National Research Council Canada Building 459, Station 18 Chalk River Laboratories Chalk River, Ontario CANADA K0J 1J0 Pho:613-584-8811 x6237 Fax:613-584-4040 http://neutron.nrc-cnrc.gc.ca/people/harroun _______________________________________________ Help-gsl mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-gsl
