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HistoChiSquare.h

Go to the documentation of this file.

#ifndef PhysicsTools_Utilities_HistoChiSquare_h
#define PhysicsTools_Utilities_HistoChiSquare_h
#include <vector>
#include "TH1.h"

namespace fit {
  template<typename T>
  class HistoChiSquare {
   public:
    HistoChiSquare() { }
    HistoChiSquare(T & t, TH1 *histo, double rangeMin, double rangeMax): 
      t_(&t), rangeMin_(rangeMin), rangeMax_(rangeMax) { 
      nBins_ = histo->GetNbinsX();
      xMin_ = histo->GetXaxis()->GetXmin();
      xMax_ = histo->GetXaxis()->GetXmax();
      deltaX_ =(xMax_ - xMin_) / nBins_;
      for(size_t i = 0; i < nBins_; ++i) { 
        cont_.push_back( histo->GetBinContent(i+1) );
        err_.push_back( histo->GetBinError(i+1) );
      }
    }
    double operator()() const { 
      double chi2 = 0;
      for(size_t i = 0; i < nBins_; ++i) { 
        double x = xMin_ + ( i +.5 ) * deltaX_;
        if((x > rangeMin_)&&(x < rangeMax_)&&(err_[i] > 0)) { 
          double r = ( cont_[i] - (*t_)(x) )/err_[i];
          chi2 += (r * r);
        }
      }
     return chi2;
    }
    void setHistos(TH1 *histo) { 
      nBins_ = histo->GetNbinsX();
      xMin_ = histo->GetXaxis()->GetXmin();
      xMax_ = histo->GetXaxis()->GetXmax();
      deltaX_ =(xMax_ - xMin_) / nBins_;
    }
    size_t degreesOfFreedom() const {
      size_t fullBins = 0;
      for(size_t i = 0; i < nBins_; ++i) { 
        double x = xMin_ + ( i +.5 ) * deltaX_;
        if((x > rangeMin_)&&(x < rangeMax_)&&(err_[i] > 0))  
          fullBins++;
      }
      return fullBins; 
    }
    T & function() { return * t_; }
    const T & function() const { return * t_; }
  private:
    T * t_;
    double rangeMin_, rangeMax_;
    size_t nBins_;
    double xMin_, xMax_, deltaX_;
    std::vector<double> cont_;
    std::vector<double> err_;
  };
}

#endif

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