Basic concepts - The transformation for parameters with limits.įor variable parameters with limits, MINUIT uses the following transformation: It is the task of MINUIT to find those values of the parameters which give the lowest value of chisquare. H1FitChisquare calculates the chisquare between the user fitting function (gaussian, polynomial, user defined,etc) and the data for given values of the parameters. To take a simple example, in case of ROOT histograms (classes TH1C, TH1S, TH1F, TH1D) the Fit function defines the Minuit fitting function as being H1FitChisquare or H1FitLikelihood depending on the options selected. The value of FCN will in general depend on one or more variable parameters. In the ROOT implementation, the function FCN is defined via the MINUIT SetFCN member function when an Histogram.Fit command is invoked. The MINUIT package acts on a multiparameter Fortran function to which one must give the generic name FCN. The functions SetObjectFit(TObject * obj)/GetObjectFit() can be used inside the FCN function to set/get a referenced object instead of using global variables.The ROOT static function Printf is provided to replace all format statements and to print on currently defined output file.The member function SetFCN can be used to define this pointer. This is by far more elegant and flexible in an interactive environment. Instead of passing the FCN function in the argument list, the addresses of this function is stored as pointer in the data members of the class.Constructors and destructor have been added.The original Minuit subroutines are now member functions.The include file Minuit.h has been commented as much as possible using existing comments in the code or the printed documentation.The internal arrays with a maximum dimension depending on the maximum number of parameters are now data members arrays with a dynamic dimension such that one can fit very large problems by simply initialising the TMinuit constructor with the maximum number of parameters. ![]() The variables in the various Minuit labelled common blocks have been changed to the TMinuit class data members.Thjis is a straightforward conversion of the original Fortran version. Implementation in C++ of the Minuit package written by F.
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