G4StatDouble.cc

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// $Id:$
// GEANT4 tag $Name: not supported by cvs2svn $
//
// 
// ----------------------------------------------------------------------
// class G4StatDouble
//
// Implementation.
// Original Author: Giovanni Santin (ESA) - October 2005 in GRAS tool
// Adapted by: John Apostolakis - November 2011

#include "G4StatDouble.hh"

G4StatDouble::G4StatDouble()
{
  reset();
}

void G4StatDouble::reset()
{
  m_sum_wx  = 0.;
  m_sum_wx2 = 0.;
  m_n       = 0;
  m_sum_w   = 0.;
  m_sum_w2  = 0.;
  m_scale   = 1.;
}

G4StatDouble::~G4StatDouble()
{}

void G4StatDouble::fill(G4double value, G4double weight)
{
  m_sum_wx  += value * weight;
  m_sum_wx2 += value * value * weight;
  m_n++;
  m_sum_w   += weight;
  m_sum_w2  += weight * weight;

  if (weight <= 0.)
  {
    G4cout << "[G4StatDouble::fill] WARNING: weight<=0. "
           << weight << G4endl;
  }
}

void G4StatDouble::scale(G4double value)
{
  m_scale = m_scale * value;
}

G4double G4StatDouble::mean() const
{
  G4double mean_val = 0.;
  if (m_sum_w > 0.)
  {
    mean_val = m_sum_wx / m_sum_w;
  }
  return m_scale * mean_val;
}

G4double G4StatDouble::mean(G4double ext_sum_w) const
{
  G4double factor = 0.;
    // factor to rescale the Mean for the requested number
    // of events (or sum of weights) ext_sum_w

  if (ext_sum_w > 0)
  {
    factor  = m_sum_w;
    factor /= ext_sum_w;
  }
  return mean() * factor;

}

G4double G4StatDouble::rms(G4double ssum_wx, G4double ssum_wx2,
                           G4double ssum_w, G4int nn)
{
  G4double vrms;
  if (nn > 1)
  {
    G4double vmean = ssum_wx / ssum_w;
    G4double xn = nn;
    G4double tmp = 
      // from GNU Scientific Library. This part is equivalent to N/(N-1)
      // when w_i = w
      // ((m_sum_w * m_sum_w) / (m_sum_w * m_sum_w - m_sum_w2)) 

      // from NIST "DATAPLOT Reference manual", Page 2-66 
      // http://www.itl.nist.gov/div898/software/dataplot/refman2/ch2/weightsd.pdf
      // rewritten based on: SUM[w(x-m)^2]/SUM[w] = SUM[wx^2]/SUM[w] - m^2
      // and dividing it by sqrt[n] to go from rms of distribution to the
      // rms of the mean value

      (1. / (xn - 1))
      * ((ssum_wx2 / ssum_w) - (vmean * vmean));

    if (tmp < 0.) tmp=0.; // this avoids observed computation problem
    vrms = std::sqrt( tmp );
//  G4cout << "[G4StatDoubleElement::rms] m_sum_wx: " << m_sum_wx
//         << "  m_sum_wx2: " << m_sum_wx2 << "  m_sum_w: " << m_sum_w
//         << "  m_n: " << m_n << "  tmp: " << tmp<< "  rms: " << rms
//         << G4endl;
//  G4cout << "[G4StatDoubleElement::rms] (m_n / (m_n - 1)): " << (xn/(xn - 1))
//     << "  (m_sum_wx2 / m_sum_w): " << (m_sum_wx2 / m_sum_w) 
//     << "  (mean * mean): " << (mean * mean) 
//     << "  ((m_sum_wx2 / m_sum_w) - (mean * mean)): "
//         << ((m_sum_wx2 / m_sum_w) - (mean * mean)) 
//     << G4endl;
  }
  else
  {
    vrms = -1.;
  }
  return vrms * m_scale;
}

G4double G4StatDouble::rms()
{
  // this method computes the RMS with "all internal" parameters:
  // all the sums are the internal ones: m_sum_wx, m_sum_wx2, m_sum_w, m_n

  return rms(m_sum_wx, m_sum_wx2, m_sum_w, m_n);
}

G4double G4StatDouble::rms(G4double ext_sum_w, G4int ext_n)
{
  // this method computes the RMS with sum_w and n coming from outside:
  // ext_sum_w and ext_n:
  // this means that the result is normalised to the external events
  // it is useful when, given a number ext_n of events with sum of the weights
  // ext_sum_w, only m_n (with sum of weights m_sum_w) are actually accumulated
  // in the internal summation (e.g. for a dose variable in a volume, because
  // only a few particles reach that volume) 

  return rms(m_sum_wx, m_sum_wx2, ext_sum_w, ext_n);
}