// @(#)root/physics:$Name:  $:$Id: TFeldmanCousins.h,v 1.5 2004/02/13 14:27:00 rdm Exp $
// Author: Adrian Bevan  2001

/*************************************************************************
 * Copyright (C) 1995-2004, Rene Brun and Fons Rademakers.               *
 * Copyright (C) 2001, Liverpool University.                             *
 * All rights reserved.                                                  *
 *                                                                       *
 * For the licensing terms see $ROOTSYS/LICENSE.                         *
 * For the list of contributors see $ROOTSYS/README/CREDITS.             *
 *************************************************************************/

#ifndef ROOT_TFeldmanCousins
#define ROOT_TFeldmanCousins

////////////////////////////////////////////////////////////////////////////
// TFeldmanCousins
//
// class to calculate the CL upper limit using
// the Feldman-Cousins method as described in PRD V57 #7, p3873-3889
//
// The default confidence interval calvculated using this method is 90%
// This is set either by having a default the constructor, or using the
// appropriate fraction when instantiating an object of this class (e.g. 0.9)
//
// The simple extension to a gaussian resolution function bounded at zero
// has not been addressed as yet -> `time is of the essence' as they write
// on the wall of the maze in that classic game ...
//
//    VARIABLES THAT CAN BE ALTERED
//    -----------------------------
// => depending on your desired precision: The intial values of fMuMin,
// fMuMax, fMuStep and fNMax are those used in the PRD:
//   fMuMin = 0.0
//   fMuMax = 50.0
//   fMuStep= 0.005
// but there is total flexibility in changing this should you desire.
//
// Author: Adrian Bevan, Liverpool University
//
// Copyright Liverpool University 2001       bevan@slac.stanford.edu
///////////////////////////////////////////////////////////////////////////

#include "TMath.h"
#include "TObject.h"
#include "TString.h"

class TFeldmanCousins : public TObject {
protected:
  Double_t fCL;         // confidence level as a fraction [e.g. 90% = 0.9]
  Double_t fUpperLimit; // the calculated upper limit
  Double_t fLowerLimit; // the calculated lower limit
  Double_t fNobserved;  // input number of observed events
  Double_t fNbackground;// input number of background events
  Double_t fMuMin;      // minimum value of signal to use in calculating the tables
  Double_t fMuMax;      // maximum value of signal to use in calculating the tables
  Double_t fMuStep;     // the step in signal to use when generating tables
  Int_t    fNMuStep;    // = (int)(fMuStep)
  Int_t    fNMax;       // = (int)(fMuMax)
  Int_t    fQUICK;      // take a short cut to speed up the process of generating a
                        // lut.  This scans from Nobserved-Nbackground-fMuMin upwards
                        // assuming that UL > Nobserved-Nbackground.

  ////////////////////////////////////////////////
  // calculate the poissonian probability for   //
  // a mean of mu+B events with a variance of N //
  ////////////////////////////////////////////////
  Double_t Prob(Int_t N, Double_t mu, Double_t B);

  ////////////////////////////////////////////////
  // calculate the probability table and see if //
  // fNObserved is in the 100.0 * fCL %         //
  // interval                                   //
  ////////////////////////////////////////////////
  Int_t FindLimitsFromTable(Double_t mu);

public:
  TFeldmanCousins(Double_t newCL=0.9, TString options = "");
  virtual ~TFeldmanCousins();

  ////////////////////////////////////////////////
  // calculate the upper limit given Nobserved  //
  // and Nbackground events                     //
  // the variables fUpperLimit and fLowerLimit  //
  // are set before returning the upper limit   //
  ////////////////////////////////////////////////
  Double_t CalculateUpperLimit(Double_t Nobserved, Double_t Nbackground);
  Double_t CalculateLowerLimit(Double_t Nobserved, Double_t Nbackground);

  inline Double_t GetUpperLimit(void) { return fUpperLimit;  }
  inline Double_t GetLowerLimit(void) { return fLowerLimit;  }
  inline Double_t GetNobserved(void)  { return fNobserved;   }
  inline Double_t GetNbackground(void){ return fNbackground; }
  inline Double_t GetCL(void)         { return fCL;          }

  inline Double_t GetMuMin(void)      { return fMuMin;  }
  inline Double_t GetMuMax(void)      { return fMuMax;  }
  inline Double_t GetMuStep(void)     { return fMuStep; }
  inline Double_t GetNMax(void)       { return fNMax;   }

  inline void SetNobserved(Double_t NObs)         { fNobserved   = NObs;  }
  inline void SetNbackground(Double_t Nbg)        { fNbackground = Nbg;   }
  inline void SetCL(Double_t newCL)               { fCL          = newCL; }

  inline void SetMuMin(Double_t  newMin    = 0.0)   { fMuMin = newMin;  }
         void SetMuMax(Double_t  newMax    = 50.0);
         void SetMuStep(Double_t newMuStep = 0.005);

  ClassDef(TFeldmanCousins,1)
};

#endif