SubsetStat.cxx

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/***************************************************************************
        
 Simple statistics object for internal alignment use

 ***************************************************************************/

#include "SubsetStat.h"

#include <cmath>
#include <iostream>

SubsetStat::SubsetStat()
   :size(0),
    sum(0.0),
    sum2(0.0)
{
}

void SubsetStat::Fill(const double &value)
{
   size++;
   sum  += value;
   sum2 += value*value;   
}


double SubsetStat::GetMean() const
{
   if(size < 1) return 0.0;

   //calculate mean
   const double mean = sum/double(size);

   return mean;
}

double SubsetStat::GetSigma() const
{
   if(size < 2) return 0.0;
      
   //calculate standard deviation
   const double size_tmp = size;
   const double sigma    = (size_tmp*sum2 - sum*sum)/(size_tmp*(size_tmp-1.0));

   if(sigma < 0.0)
   {
      std::cout << "Floating point error: sigma can not be negative!" << std::endl;
      return 0.0;
   }

   return std::pow(sigma, 0.5);
}

void SubsetStat::Reset()
{
   size = 0;
   sum  = 0.0;
   sum = 0.0;
}

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