CombinedChiSquaredLikelihood.h

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#ifndef PhysicsTools_Utilities_CombinedChiSquaredLikelihood_h
#define PhysicsTools_Utilities_CombinedChiSquaredLikelihood_h
#include "PhysicsTools/Utilities/interface/RootMinuitResultPrinter.h"
#include "PhysicsTools/Utilities/interface/RootMinuitFuncEvaluator.h"

namespace fit {
  template <typename ChiSquared, typename Likelihood>
  class CombinedChiSquaredLikelihood {
  public:
    CombinedChiSquaredLikelihood() {}
    CombinedChiSquaredLikelihood(const ChiSquared& chi2, const Likelihood& like) : chi2_(chi2), like_(like) {}
    // return chi-square value
    double operator()() const { return -2 * like_() + chi2_(); }
    ChiSquared& chi2() { return chi2_; }
    const ChiSquared& chi2() const { return chi2_; }
    Likelihood& like() { return like_; }
    const Likelihood& like() const { return like_; }
    size_t numberOfBins() const { return chi2_.numberOfBins(); }

  private:
    ChiSquared chi2_;
    Likelihood like_;
  };

  template <typename ChiSquared, typename Likelihood>
  struct RootMinuitResultPrinter<CombinedChiSquaredLikelihood<ChiSquared, Likelihood> > {
    static void print(double amin,
                      unsigned int numberOfFreeParameters,
                      const CombinedChiSquaredLikelihood<ChiSquared, Likelihood>& f) {
      unsigned int ndof = f.numberOfBins() - numberOfFreeParameters;
      std::cout << "-2 log(maximum-likelihood) = " << amin << ", n.d.o.f = " << ndof
                << ", free parameters = " << numberOfFreeParameters << std::endl;
      std::cout << "chi-2 contibution: " << f.chi2()() << "(n. bins: " << f.chi2().numberOfBins() << ")" << std::endl
                << "likelihood contriution: " << -2. * f.like()() << std::endl;
    }
  };

}  // namespace fit

#endif