JASTRONOMY::JAspera Struct Reference

Auxiliary data structure to fit signal strength using likelihood ratio. More...

#include <JAspera.hh>

Inheritance diagram for JASTRONOMY::JAspera:

Classes
struct	fit_type
	Result of fit. More...

Public Member Functions
void	put (const double s, const double b)
	Put signal and background to list of pre-computed N/S values.
void	put (const size_t n, const double s, const double b)
	Put signal and background to list of pre-computed N/S values.
double	getLikelihood (const double p) const
	Get likelihood for given signal strength.
double	getDerivative (const double p) const
	Get derivative of likelihood for given signal strength.
fit_type	operator() () const
	Fit signal strength.
double	getSignal () const
	Get total signal strength.
void	setSignal (const double wS)
	Set signal strength.
void	addSignal (const double wS)
	Add signal strength.

Static Public Attributes
static constexpr double	EPSILON = 1.0e-3
	precision determination of signal strength

Protected Attributes
double	ws = 0.0
	total signal strength

Detailed Description

Auxiliary data structure to fit signal strength using likelihood ratio.

Definition at line 22 of file JAspera.hh.

Member Function Documentation

put() [1/2]

void JASTRONOMY::JAspera::put ( const double s, const double b )

inline

Put signal and background to list of pre-computed N/S values.

Parameters

s	signal
b	background

Definition at line 44 of file JAspera.hh.

    {
      push_back(b/s);
 
      ws += s;
    }

put() [2/2]

void JASTRONOMY::JAspera::put ( const size_t n, const double s, const double b )

inline

Put signal and background to list of pre-computed N/S values.

Parameters

n	data
s	signal
b	background

Definition at line 60 of file JAspera.hh.

    {
      for (size_t i = 0; i != n; ++i) {
        push_back(b/s);
      }
 
      ws += s;
    }

getLikelihood()

double JASTRONOMY::JAspera::getLikelihood ( const double p ) const

inline

Get likelihood for given signal strength.

Parameters

p	signal strength

Returns

likelihood

Definition at line 78 of file JAspera.hh.

    {
      double y = -p * ws;
 
      for (const auto& i : static_cast<const std::vector<double>&>(*this)) {
        y += log1p(p/i);
      }
 
      if (y > 0.0)
        return y;
      else
        return 0.0;
    }

getDerivative()

double JASTRONOMY::JAspera::getDerivative ( const double p ) const

inline

Get derivative of likelihood for given signal strength.

Parameters

p	signal strength

Returns

derivative of likelihood

Definition at line 99 of file JAspera.hh.

    {
      double y = -ws;
 
      for (const auto& i : static_cast<const std::vector<double>&>(*this)) {
        y += 1.0 / (p + i);
      }
 
      return y;
    }

operator()()

fit_type JASTRONOMY::JAspera::operator() ( ) const

inline

Fit signal strength.

Returns

result

Definition at line 116 of file JAspera.hh.

    {
      using namespace std;
 
      double x1 = 0.0;                          // lower limit corresponds to no signal; less to under-fluctuation
      double x2 = (double) this->size() / ws;   // upper limit corresponds to no background (i.e. all N/S = 0)
      // bisection
      /*
      if (getDerivative(x1) > 0.0) {
 
        for ( ; ; ) {
 
          const double x = 0.5 * (x1 + x2);
 
          if (x2 - x1 <= EPSILON) {
            return { getLikelihood(x), x };
          }
 
          if (getDerivative(x) < 0.0)
            x2 = x;
          else
            x1 = x;
        }
      }
      */
      // Ridder's method
      double f1 = getDerivative(x1);
 
      if (f1 > 0.0) {
  
        double f2 = getDerivative(x2);
 
        while (x2 - x1 > EPSILON) {
 
          const double xm = 0.5 * (x1 + x2);
          const double fm = getDerivative(xm);
 
          const double s  = sqrt(fm*fm - f1*f2);
 
          if (s == 0.0) {
            break;
          }
 
          const double xn = xm + (xm - x1) * fm/s;
          const double fn = getDerivative(xn);
 
          if (signbit(fn) != signbit(fm)) {
 
            x1 = xm;
            f1 = fm;
            x2 = xn;
            f2 = fn;
 
          } else {
 
            if (signbit(fn)) {
 
              x2 = xn;
              f2 = fn;
 
            } else {
 
              x1 = xn;
              f1 = fn;
            }
          }
        }
 
        const double x = 0.5 * (x1 + x2);
 
        return { getLikelihood(x), x };
      }
      //
      return { 0.0, 0.0 };
    }

getSignal()

double JASTRONOMY::JAspera::getSignal ( ) const

inline

Get total signal strength.

Returns

signal strength

Definition at line 198 of file JAspera.hh.

    {
      return ws;
    }

setSignal()

void JASTRONOMY::JAspera::setSignal ( const double wS )

inline

Set signal strength.

Parameters

wS	signal strength

Definition at line 209 of file JAspera.hh.

    {
      ws = wS;
    }

addSignal()

void JASTRONOMY::JAspera::addSignal ( const double wS )

inline

Add signal strength.

Parameters

wS	signal strength

Definition at line 220 of file JAspera.hh.

    {
      ws += wS;
    }

Member Data Documentation

EPSILON

double JASTRONOMY::JAspera::EPSILON = 1.0e-3

staticconstexpr

precision determination of signal strength

Definition at line 26 of file JAspera.hh.

ws

double JASTRONOMY::JAspera::ws = 0.0

protected

total signal strength

Definition at line 227 of file JAspera.hh.

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The documentation for this struct was generated from the following file:

• JAspera.hh