RooHistError.h

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/*****************************************************************************
 * Project: RooFit                                                           *
 * Package: RooFitCore                                                       *
 *    File: $Id: RooHistError.h,v 1.14 2007/05/11 09:11:30 verkerke Exp $
 * Authors:                                                                  *
 *   WV, Wouter Verkerke, UC Santa Barbara, verkerke@slac.stanford.edu       *
 *   DK, David Kirkby,    UC Irvine,         dkirkby@uci.edu                 *
 *                                                                           *
 * Copyright (c) 2000-2005, Regents of the University of California          *
 *                          and Stanford University. All rights reserved.    *
 *                                                                           *
 * Redistribution and use in source and binary forms,                        *
 * with or without modification, are permitted according to the terms        *
 * listed in LICENSE (http://roofit.sourceforge.net/license.txt)             *
 *****************************************************************************/
#ifndef ROO_HIST_ERROR
#define ROO_HIST_ERROR
 
#include "Rtypes.h"
#include "RooNumber.h"
#include "RooAbsFunc.h"
#include <cmath>
#include <iostream>
 
class RooHistError {
public:
  static const RooHistError &instance();
  virtual ~RooHistError() {} ;
 
  bool getPoissonInterval(Int_t n, double &mu1, double &mu2, double nSigma= 1) const;
  bool getBinomialIntervalAsym(Int_t n, Int_t m, double &a1, double &a2, double nSigma= 1) const;
  bool getBinomialIntervalEff(Int_t n, Int_t m, double &a1, double &a2, double nSigma= 1) const;
  bool getInterval(const RooAbsFunc *Qu, const RooAbsFunc *Ql, double pointEstimate, double stepSize,
           double &lo, double &hi, double nSigma) const;
 
  static RooAbsFunc *createPoissonSum(Int_t n) ;
  static RooAbsFunc *createBinomialSum(Int_t n, Int_t m, bool eff) ;
 
private:
  double seek(const RooAbsFunc &f, double startAt, double step, double value) const;
 
  // -----------------------------------------------------------
  // Define a 1-dim RooAbsFunc of mu that evaluates the sum:
  //
  //  Q(n|mu) = Sum_{k=nullptr}^{n} P(k|mu)
  //
  // where P(n|mu) = exp(-mu) mu**n / n! is the Poisson PDF.
  // -----------------------------------------------------------
  class PoissonSum : public RooAbsFunc {
  public:
    inline PoissonSum(Int_t n) : RooAbsFunc(1), _n(n) { }
    inline double operator()(const double xvec[]) const override {
       double mu(xvec[0]);
       double result(1);
       double factorial(1);
       for (Int_t k = 1; k <= _n; k++) {
          factorial *= k;
          result += pow(mu, k) / factorial;
      }
      return exp(-mu)*result;
    };
    inline double getMinLimit(UInt_t /*index*/) const override { return 0; }
    inline double getMaxLimit(UInt_t /*index*/) const override { return RooNumber::infinity() ; }
  private:
    Int_t _n;
  };
 
  // -----------------------------------------------------------
  // Define a 1-dim RooAbsFunc of a that evaluates the sum:
  //
  //  Q(n|n+m,a) = Sum_{k=nullptr}^{n} B(k|n+m,a)
  //
  // where B(n|n+m,a) = (n+m)!/(n!m!) ((1+a)/2)**n ((1-a)/2)**m
  // is the Binomial PDF.
  // -----------------------------------------------------------
  class BinomialSumAsym : public RooAbsFunc {
  public:
    BinomialSumAsym(Int_t n, Int_t m) : RooAbsFunc(1), _n1(n), _N1(n+m) {
    }
    inline double operator()(const double xvec[]) const override
      {
      double p1(0.5 * (1 + xvec[0]));
      double p2(1 - p1);
      double result(0);
      double fact1(1);
      double fact2(1);
      for (Int_t k = 0; k <= _n1; k++) {
         if (k > 0) {
            fact2 *= k;
            fact1 *= _N1 - k + 1;
         }
         result += fact1 / fact2 * pow(p1, k) * pow(p2, _N1 - k);
   }
   return result;
      };
 
    inline double getMinLimit(UInt_t /*index*/) const override { return -1; }
    inline double getMaxLimit(UInt_t /*index*/) const override { return +1; }
 
  private:
    Int_t _n1 ; ///< WVE Solaris CC5 doesn't want _n or _N here (likely compiler bug)
    Int_t _N1 ;
  } ;
 
 
  // -----------------------------------------------------------
  // Define a 1-dim RooAbsFunc of a that evaluates the sum:
  //
  //  Q(n|n+m,a) = Sum_{k=nullptr}^{n} B(k|n+m,a)
  //
  // where B(n|n+m,a) = (n+m)!/(n!m!) ((1+a)/2)**n ((1-a)/2)**m
  // is the Binomial PDF.
  // -----------------------------------------------------------
  class BinomialSumEff : public RooAbsFunc {
  public:
    BinomialSumEff(Int_t n, Int_t m) : RooAbsFunc(1), _n1(n), _N1(n+m) {
    }
    inline double operator()(const double xvec[]) const override
      {
   double p1(xvec[0]);
   double p2(1 - p1);
   double result(0);
   double fact1(1);
   double fact2(1);
   for(Int_t k= 0; k <= _n1; k++) {
     if(k > 0) { fact2*= k; fact1*= _N1-k+1; }
     result+= fact1/fact2*pow(p1,k)*pow(p2,_N1-k);
   }
   return result;
      };
 
    inline double getMinLimit(UInt_t /*index*/) const override { return  0; }
    inline double getMaxLimit(UInt_t /*index*/) const override { return +1; }
 
  private:
    Int_t _n1 ; ///< WVE Solaris CC5 doesn't want _n or _N here (likely compiler bug)
    Int_t _N1 ;
  } ;
 
};
 
#endif