ChiSquare.h

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//*                 copied verbatim in the file "LICENSE".                   *
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//*  Copyright (C) 2006 - 2024 FAIR GmbH and copyright holders of PandaRoot  *
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// ******************************************************
// DecayTreeFitter Package
// We thank the original author Wouter Hulsbergen
// (BaBar, LHCb) for providing the sources.
// http://arxiv.org/abs/physics/0503191v1 (2005)
// Adaptation & Development for PANDA: Ralf Kliemt (2015)
// ******************************************************
#ifndef DECAYTREEFITTER_ChiSquare_H
#define DECAYTREEFITTER_ChiSquare_H 1
#include "Rtypes.h"
#include "TMath.h"

namespace DecayTreeFitter {

class ChiSquare {
 public:
  ChiSquare(const double achi2, int andof) : m_chi2(achi2), m_nDoF(andof) {}

  ChiSquare() : m_chi2(0.0), m_nDoF(0) {}

  virtual ~ChiSquare() {}

  double chi2PerDoF() const { return m_nDoF > 0 ? m_chi2 / m_nDoF : 0; }

  ChiSquare &operator+=(const ChiSquare &rhs);

  ChiSquare &operator-=(const ChiSquare &rhs);

  ChiSquare operator+(const ChiSquare &rhs);

  ChiSquare operator-(const ChiSquare &rhs);

  double chi2() const { return m_chi2; }

  int nDoF() const { return m_nDoF; }

  double prob() const { return TMath::Prob(m_chi2, m_nDoF); }

 protected:
 private:
  double m_chi2; 
  int m_nDoF;    
  ClassDef(ChiSquare, 1)

}; // class ChiSquare

inline ChiSquare &ChiSquare::operator+=(const ChiSquare &rhs)
{
  m_chi2 += rhs.m_chi2;
  m_nDoF += rhs.m_nDoF;
  return *this;
}

inline ChiSquare &ChiSquare::operator-=(const ChiSquare &rhs)
{
  m_chi2 -= rhs.m_chi2;
  m_nDoF -= rhs.m_nDoF;
  return *this;
}

inline ChiSquare ChiSquare::operator+(const ChiSquare &rhs)
{
  ChiSquare rc = *this;
  rc += rhs;
  return rc;
}

inline ChiSquare ChiSquare::operator-(const ChiSquare &rhs)
{
  ChiSquare rc = *this;
  rc -= rhs;
  return rc;
}
} // namespace DecayTreeFitter

#endif