NTupleLikeliHoodFCN.cxx

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#ifdef _MSC_VER
#include "msdevstudio/MSconfig.h"
#endif

#include "NTupleLikeliHoodFCN.h"

#include "datasrcs/DataPointTuple.h"
#include "datasrcs/DataSource.h"
#include "functions/FunctionBase.h"

#include <cmath>
#include <cassert>

using std::vector;
using std::log;
using std::pow;
using std::exp;

NTupleLikeliHoodFCN::
NTupleLikeliHoodFCN ()
{
}

NTupleLikeliHoodFCN::
NTupleLikeliHoodFCN ( const NTupleLikeliHoodFCN & fcn )
  : NTupleFCN ( fcn )
{
}

StatedFCN *
NTupleLikeliHoodFCN::
clone () const
{
  return new NTupleLikeliHoodFCN ( *this );
}

namespace dp = hippodraw::DataPoint2DTuple;

double
NTupleLikeliHoodFCN::
objectiveValue () const
{
  double result = 0.0;
  double sum1 = 0.0;
  double sum2 = 0.0;

  int ix = m_indices [ dp::X ];
  int iy = m_indices [ dp::Y ];
  int ie = m_indices [ dp::XERR ];
  
  int num_bins = m_ntuple -> rows ();
  for( int i = 0; i < num_bins; i++ )
    {
      if ( acceptRow ( i )  ) {
        const vector < double > & row = m_ntuple -> getRow ( i );
      
        // Get the edges of the bin.
        double x = row [ ix ];
        double hwidth = 0.5 * row [ ie ];
        double edgeL = x - hwidth;
        double edgeR = x + hwidth;
      
        // Integrate function over the entire i-th bin
        double theta = m_function-> integrate( edgeL, edgeR );
            
        // Get number of enteries in the ith bin
        double n = 2.0 * hwidth * row [ iy ];
      
        // Computing the factorial of n and taking log of it.
        // Exact computation is done when N is small ( < 100) else
        // we use sterliing's approximations for it.
        // CAUTION: Exactly calculating factorial itself usually leads to
        // a very large and unrepresentable number so we avoid it.
        //double logfactn = 0.0;
        //if( n < 100 )
        //{
        //  
        //  for( int j = 2; j <= n; j++)
        //    logfactn += log( (double) j );
        //  
        //  result += ( n * log ( theta ) - theta - logfactn   );
        //}
        //else
        //{
        //  logfactn = n * log( (double) n ) - n;
        //  result +=( n * ( log ( theta ) - log( (double) n ) + 1 ) - theta );
        //}

        //result += ( n * log ( theta ) - theta );
      
        sum1 += n * log ( theta );
        sum2 += theta;
      
      }
    }
  result = sum1 - sum2;
  // The quantity that is (asymptotically) equivalent to
  // chi-square is -2 log( L ) i.e we return  -2 * result
  
  return ( -2 * result );  
}

bool
NTupleLikeliHoodFCN::
needsIntegrated () const
{
  return true;
}

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