HistoPdf.h

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#ifndef PhysicsTools_Utilities_HistoPdf_h
#define PhysicsTools_Utilities_HistoPdf_h

#include "FWCore/Utilities/interface/EDMException.h"

#include <iostream>
#include "TH1.h"

namespace funct {
  class HistoPdf {
  public:
    template<typename Iterator>
    HistoPdf(double xMin, double xMax, 
         const Iterator & begin, const Iterator & end) :
      xMin_(xMin), xMax_(xMax), delta_(xMax - xMin), binSize_(delta_ / (end - begin)), y_(end - begin) {
      double s = 0;
      unsigned int i = 0;
      for(Iterator it = begin; it != end; ++it)
    s += (y_[i++] = *it);
      for(std::vector<double>::iterator i = y_.begin(); i != y_.end(); ++i)
    *i /= s;
    }
    HistoPdf() { }
    template<typename Iterator>
    void init(double xMin, double xMax, 
          const Iterator & begin, const Iterator & end) {
      xMin_ = xMin;
      xMax_ = xMax;
      delta_ = xMax - xMin;
      unsigned int n = end - begin;
      binSize_ = delta_ / n;
      y_.resize(n);
      double s = 0;
      unsigned int i = 0;
      for(Iterator it = begin; it != end; ++it)
    s += (y_[i++] = *it);
      for(std::vector<double>::iterator i = y_.begin(); i != y_.end(); ++i)
    *i /= s;
    }
    double operator()(double x) const {
      if (x < xMin_ || x > xMax_) return 0;
      double pdf = y_[static_cast<unsigned int>(((x -xMin_)/delta_)*y_.size())] / binSize_;
      return pdf;
    }
    void rebin(unsigned int r) {
      if(y_.size() % r != 0) 
    throw edm::Exception(edm::errors::Configuration) <<
      "HistoPdf: can't rebin histogram of " << y_.size() << " entries by " << r << "\n";
      unsigned int n = y_.size() / r;
      std::vector<double> y(n, 0);
      for(unsigned int i = 0, j = 0; i < n; ++i)
    for(unsigned int k = 0; k < r; ++k) 
      y[i] += y_[j++];
      y_ = y;
      binSize_ *= r;
    }
    void dump() {
      std::cout << ">>> range: [" << xMin_ << ", " << xMax_ << "], bin size: " 
       << delta_ << "/" << y_.size() << " = " << binSize_ << std::endl;
       double s = 0;
      for(unsigned int i = 0; i != y_.size(); ++i) {
    double x = xMin_ + (0.5 + i)*binSize_;
    double y = operator()(x);
    std::cout << ">>> pdf(" << x << ") = " << y << std::endl;
    s+= y*binSize_;
      }
     std::cout << ">>>: PDF normalization is " << s << std::endl;
    }
  private:
    double xMin_, xMax_, delta_, binSize_;
    std::vector<double> y_;
  };

  class RootHistoPdf : public HistoPdf {
  public:
    explicit RootHistoPdf(const TH1 & histo, double fMin, double fMax) {
      unsigned int nBins = histo.GetNbinsX();
      std::vector<double> y;      
      y.reserve(nBins);
      double xMin = histo.GetXaxis()->GetXmin();
      double xMax = histo.GetXaxis()->GetXmax();
      double deltaX =(xMax - xMin) / nBins;
      for(unsigned int i = 0; i != nBins; ++i) {
    double x = xMin + (i + .5) * deltaX;
    if(x > fMin && x < fMax) {
      y.push_back(histo.GetBinContent(i+1));
    }
      }
      init(fMin, fMax, y.begin(), y.end());
    }
  };

}


#endif