IncompleteGammaComplement Class Reference

#include <IncompleteGammaComplement.h>

Static Public Member Functions
static float	ln (float a, float x)
static float	value (float a, float x)

Detailed Description

Computes the complement Q(a,x)=1-P(a,x) of the incomplete gamma function. Computes its natural logarithm, useful for comparing very small values. source: Numerical Recipes

Definition at line 9 of file IncompleteGammaComplement.h.

Member Function Documentation

float IncompleteGammaComplement::ln ( float  a, float  x  )

static

Definition at line 25 of file IncompleteGammaComplement.cc.

References create_public_lumi_plots::exp, GammaContinuedFraction(), GammaLn(), GammaSeries(), and dqm-mbProfile::log.

Referenced by LnChiSquaredProbability().

{
  if( x < 0.0 || a <= 0.0 ) 
edm::LogInfo("IncompleteGammaComplement")<< "IncompleteGammaComplement::invalid arguments";
  if( x < (a+1.0) )
    // take the complement of the series representation    
    return log(1.-GammaSeries(a,x)*(exp(-x + a*log(x) - GammaLn(a))));
  else
    // use the continued fraction representation
    return log(GammaContinuedFraction(a,x)) -x + a*log(x) - GammaLn(a);
}

float IncompleteGammaComplement::value ( float  a, float  x  )

static

Definition at line 12 of file IncompleteGammaComplement.cc.

References create_public_lumi_plots::exp, GammaContinuedFraction(), GammaLn(), GammaSeries(), and dqm-mbProfile::log.

Referenced by average.Average::average(), and ChiSquaredProbability().

{
  if( x < 0.0 || a <= 0.0 ) 
    edm::LogInfo("IncompleteGammaComplement")<< "IncompleteGammaComplement::invalid arguments";
  if( x < (a+1.0) )
    // take the complement of the series representation
    return 1.-GammaSeries(a,x)*(exp(-x + a*log(x) - GammaLn(a)));
  else
    // use the continued fraction representation
    return GammaContinuedFraction(a,x)*(exp(-x + a*log(x) - GammaLn(a)));
}