Minimum finder using tabulated chi^2 values in one dimension. More...

#include <Chi2MinimumFinder1D.h>

Classes
struct	Minimum
	Result of minimum finder. More...

Public Member Functions
	Chi2MinimumFinder1D ()
	Default constructor.

	Chi2MinimumFinder1D (int nbins, double xmin, double xmax)
	Class constructor, similar to 1D histogram.

	Chi2MinimumFinder1D (const std::shared_ptr< TH1D > h)
	Constructor from a histogram.

void	clear ()
	Set chi^2 values to zero.

void	add (unsigned i, double chi2)
	Add chi^2 value to bin i.

Chi2MinimumFinder1D &	add (const Chi2MinimumFinder1D &other)
	Add data from another finder Finders must be defined with the same range and binning.

double	getXmin () const
	Returns lower limit of search region.

double	getXmax () const
	Returns upper limit of search region.

int	getNbins () const
	Returns number of bins.

double	getBinSize () const
	Returns bin (or step) size.

const std::vector< double > &	getBinCenters () const
	Returns vector of bin centers.

const std::vector< double > &	getChi2Values () const
	Returns vector of chi^2.

double	getMinChi2 () const
	Returns minimum chi2 value.

int	getEntries () const
	Returns number of entries (counted for bin 0)

const Minimum &	getMinimum ()
	Returns parabolic minimum.

TH1F	getHistogram (std::string name, std::string title) const
	Returns chi^2 packed into 1D histogram.

Private Member Functions
void	findMinimum ()
	Finds minimum.

Minimum	getMinimum (double yLeft, double yCenter, double yRight) const
	Calculates minimum using parabolic interpolation.

Private Attributes
double	m_xmin = 0
	lower limit of search region

double	m_xmax = 0
	upper limit of search region

double	m_dx = 0
	bin size

std::vector< double >	m_x
	bin centers

std::vector< double >	m_chi2
	chi^2 values at bin centers

int	m_entries = 0
	number of entries (counted for bin 0)

bool	m_searched = false
	internal flag

Minimum	m_minimum
	result: global minimum

Detailed Description

Minimum finder using tabulated chi^2 values in one dimension.

Definition at line 28 of file Chi2MinimumFinder1D.h.

Constructor & Destructor Documentation

◆ Chi2MinimumFinder1D() [1/3]

Chi2MinimumFinder1D ( )

inline

Default constructor.

Definition at line 58 of file Chi2MinimumFinder1D.h.

59 {}

◆ Chi2MinimumFinder1D() [2/3]

Chi2MinimumFinder1D	(	int	nbins,
		double	xmin,
		double	xmax
	)

Class constructor, similar to 1D histogram.

Parameters

nbins	number of points the search region is divided to
xmin	lower limit of the search region
xmax	upper limit of the search region

Definition at line 22 of file Chi2MinimumFinder1D.cc.

                                                                               :
      m_xmin(xmin), m_xmax(xmax)
    {
      if (nbins <= 0) {
        B2ERROR("Chi2MinimumFinder1D: nbins must be positive integer");
        return;
      }
      if (m_xmax <= m_xmin) {
        B2ERROR("Chi2MinimumFinder1D: search range max < min");
        return;
      }
      m_dx = (m_xmax - m_xmin) / nbins;
      double x = m_xmin + m_dx / 2;
      while (x < m_xmax) {
        m_x.push_back(x);
        x += m_dx;
      }
      m_chi2.resize(m_x.size(), 0);
    }

◆ Chi2MinimumFinder1D() [3/3]

Chi2MinimumFinder1D ( const std::shared_ptr< TH1D > h )

explicit

Constructor from a histogram.

Definition at line 42 of file Chi2MinimumFinder1D.cc.

    {
      m_xmin = h->GetXaxis()->GetXmin();
      m_xmax = h->GetXaxis()->GetXmax();
      m_dx = h->GetBinWidth(1);
      for (int i = 0; i < h->GetNbinsX(); i++) {
        m_x.push_back(h->GetBinCenter(i + 1));
        m_chi2.push_back(h->GetBinContent(i + 1));
      }
      m_entries = h->GetEntries() / h->GetNbinsX();
    }

Member Function Documentation

◆ add() [1/2]

Chi2MinimumFinder1D & add ( const Chi2MinimumFinder1D & other )

Add data from another finder Finders must be defined with the same range and binning.

Returns: a reference to this finder

Definition at line 74 of file Chi2MinimumFinder1D.cc.

    {
      if (m_x.empty()) {
        *this = other;
      } else if (other.getBinCenters().size() == m_x.size() and other.getXmin() == m_xmin and other.getXmax() == m_xmax) {
        const auto& chi2 = other.getChi2Values();
        for (unsigned i = 0; i < m_chi2.size(); i++) {
          m_chi2[i] += chi2[i];
        }
        m_entries += other.getEntries();
        m_searched = false;
      } else {
        B2ERROR("Chi2MinimumFinder1D::add: finders with different ranges or binning can't be added");
      }
 
      return *this;
    }

◆ add() [2/2]

void add	(	unsigned	i,
		double	chi2
	)

Add chi^2 value to bin i.

Parameters

i	bin index (0-based)
chi2	value to be added

Definition at line 62 of file Chi2MinimumFinder1D.cc.

    {
      if (i < m_chi2.size()) {
        m_chi2[i] += chi2;
        m_searched = false;
        if (i == 0) m_entries++;
      } else {
        B2WARNING("Chi2MinimumFinder1D::add: index out of range");
      }
    }

◆ clear()

void clear ( )

Set chi^2 values to zero.

Definition at line 54 of file Chi2MinimumFinder1D.cc.

    {
      for (auto& chi2 : m_chi2) chi2 = 0;
      m_entries = 0;
      m_searched = false;
    }

◆ findMinimum()

void findMinimum ( )

private

Finds minimum.

Definition at line 93 of file Chi2MinimumFinder1D.cc.

    {
      if (m_chi2.size() < 3) {
        m_minimum.position = (m_xmin + m_xmax) / 2;
        m_minimum.error = (m_xmax - m_xmin) / 2;
        return;
      }
 
      unsigned i0 = 1;
      for (unsigned i = i0; i < m_chi2.size() - 1; i++) {
        if (m_chi2[i] < m_chi2[i0]) i0 = i;
      }
      auto x = getMinimum(m_chi2[i0 - 1], m_chi2[i0], m_chi2[i0 + 1]);
      m_minimum = Minimum(m_x[i0] + x.position * m_dx, x.error * m_dx, x.chi2, x.valid);
    }

◆ getBinCenters()

const std::vector< double > & getBinCenters ( ) const

inline

Returns vector of bin centers.

Returns: bin centers

Definition at line 121 of file Chi2MinimumFinder1D.h.

121{return m_x;}

◆ getBinSize()

double getBinSize ( ) const

inline

Returns bin (or step) size.

Returns: bin size

Definition at line 115 of file Chi2MinimumFinder1D.h.

115{return m_dx;}

◆ getChi2Values()

const std::vector< double > & getChi2Values ( ) const

inline

Returns vector of chi^2.

Returns: chi^2 values

Definition at line 127 of file Chi2MinimumFinder1D.h.

127{return m_chi2;}

◆ getEntries()

int getEntries ( ) const

inline

Returns number of entries (counted for bin 0)

Returns: number of entries

Definition at line 140 of file Chi2MinimumFinder1D.h.

140{return m_entries;}

◆ getHistogram()

TH1F getHistogram	(	std::string	name,
		std::string	title
	)		const

Returns chi^2 packed into 1D histogram.

Parameters

name	histogram name
title	histogram title

Definition at line 126 of file Chi2MinimumFinder1D.cc.

    {
      TH1F h(name.c_str(), title.c_str(), m_x.size(), m_xmin, m_xmax);
      for (unsigned i = 0; i < m_chi2.size(); i++) {
        h.SetBinContent(i + 1, m_chi2[i] - m_minimum.chi2);
      }
      return h;
    }

◆ getMinChi2()

double getMinChi2 ( ) const

inline

Returns minimum chi2 value.

Returns: minimum chi2 value

Definition at line 134 of file Chi2MinimumFinder1D.h.

134{return *std::min_element(m_chi2.begin(), m_chi2.end());}

◆ getMinimum() [1/2]

const Minimum & getMinimum ( )

inline

Returns parabolic minimum.

Definition at line 145 of file Chi2MinimumFinder1D.h.

      {
        if (!m_searched) {
          findMinimum();
          m_searched = true;
        }
        return m_minimum;
      }

◆ getMinimum() [2/2]

Chi2MinimumFinder1D::Minimum getMinimum	(	double	yLeft,
		double	yCenter,
		double	yRight
	)		const

private

Calculates minimum using parabolic interpolation.

Parameters

yLeft	bin content of left-to-minimal bin
yCenter	bin content of minimal bin
yRight	bin content of right-to-minimal bin

Returns: minimum given as a fraction of step to be added to central bin position

Definition at line 110 of file Chi2MinimumFinder1D.cc.

    {
      // parabola: y = ax^2 + bx + c
      double DL = yLeft - yCenter;
      double DR = yRight - yCenter;
      double A = (DR + DL) / 2;
      if (A <= 0) return Minimum(0, 0, yCenter, false);
      double B = (DR - DL) / 2;
      double x = - B / 2 / A;
      double chi2_min = A * x * x + B * x + yCenter;
      return Minimum(x, sqrt(1 / A), chi2_min, true);
    }

◆ getNbins()

int getNbins ( ) const

inline

Returns number of bins.

Returns: number of bins

Definition at line 109 of file Chi2MinimumFinder1D.h.

109{return m_x.size();}

◆ getXmax()

double getXmax ( ) const

inline

Returns upper limit of search region.

Returns: xmax

Definition at line 103 of file Chi2MinimumFinder1D.h.

103{return m_xmax;}

◆ getXmin()

double getXmin ( ) const

inline

Returns lower limit of search region.

Returns: xmin

Definition at line 97 of file Chi2MinimumFinder1D.h.

97{return m_xmin;}

Member Data Documentation

◆ m_chi2

std::vector<double> m_chi2

private

chi^2 values at bin centers

Definition at line 182 of file Chi2MinimumFinder1D.h.

◆ m_dx

double m_dx = 0

private

bin size

Definition at line 180 of file Chi2MinimumFinder1D.h.

◆ m_entries

int m_entries = 0

private

number of entries (counted for bin 0)

Definition at line 183 of file Chi2MinimumFinder1D.h.

◆ m_minimum

Minimum m_minimum

private

result: global minimum

Definition at line 186 of file Chi2MinimumFinder1D.h.

◆ m_searched

bool m_searched = false

private

internal flag

Definition at line 185 of file Chi2MinimumFinder1D.h.

◆ m_x

std::vector<double> m_x

private

bin centers

Definition at line 181 of file Chi2MinimumFinder1D.h.

◆ m_xmax

double m_xmax = 0

private

upper limit of search region

Definition at line 178 of file Chi2MinimumFinder1D.h.

◆ m_xmin

double m_xmin = 0

private

lower limit of search region

Definition at line 177 of file Chi2MinimumFinder1D.h.

The documentation for this class was generated from the following files:

top/utilities/include/Chi2MinimumFinder1D.h
top/utilities/src/Chi2MinimumFinder1D.cc

Classes

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

Constructor & Destructor Documentation

◆ Chi2MinimumFinder1D() [1/3]

◆ Chi2MinimumFinder1D() [2/3]

◆ Chi2MinimumFinder1D() [3/3]

Member Function Documentation

◆ add() [1/2]

◆ add() [2/2]

◆ clear()

◆ findMinimum()

◆ getBinCenters()

◆ getBinSize()

◆ getChi2Values()

◆ getEntries()

◆ getHistogram()

◆ getMinChi2()

◆ getMinimum() [1/2]

◆ getMinimum() [2/2]

◆ getNbins()

◆ getXmax()

◆ getXmin()

Member Data Documentation

◆ m_chi2

◆ m_dx

◆ m_entries

◆ m_minimum

◆ m_searched

◆ m_x

◆ m_xmax

◆ m_xmin