FacetFitter Class Reference

Utility class to fit hit triplet and relations of them. More...

#include <FacetFitter.h>

Static Public Member Functions
static double	fit (const TrackingUtilities::CDCFacet &facet, int nSteps=100, double maxChi2=std::numeric_limits< double >::infinity())
	Fits a proper line to the facet and returns the chi2.
static TrackingUtilities::UncertainParameterLine2D	fit (const TrackingUtilities::CDCFacet &fromFacet, const TrackingUtilities::CDCFacet &toFacet, int nSteps=100)
	Fit a line the positions xyl and the weights.
static double	fitChi2 (const TrackingUtilities::CDCFacet &fromFacet, const TrackingUtilities::CDCFacet &toFacet)
	Calculate only the chi2 of a line fitted to the hits of the two facets.
static TrackingUtilities::UncertainParameterLine2D	fit (TrackingUtilities::Matrix< double, 3, 3 > xyl, TrackingUtilities::Matrix< double, 3, 1 > w, int nSteps=100)
	Fit a line the positions xyl and the weights.

Detailed Description

Utility class to fit hit triplet and relations of them.

Definition at line 26 of file FacetFitter.h.

Member Function Documentation

fit() [1/3]

double fit ( const TrackingUtilities::CDCFacet & facet, int nSteps = 100, double maxChi2 = std::numeric_limits<double>::infinity() )

static

Fits a proper line to the facet and returns the chi2.

The fitted line is committed to the facet only if its chi2 is at most maxChi2. With the default maxChi2 = infinity the line is always committed; passing a finite maxChi2 skips the construction of the line and its covariance matrix for facets that fail the cut anyway.

Definition at line 263 of file FacetFitter.cc.

{
  // Measurement matrix
  Matrix<double, 3, 3> xyl = Matrix<double, 3, 3>::Zero();
 
  // Weight matrix
  Matrix<double, 3, 1> w = Matrix<double, 3, 1>::Zero();
 
  const ROOT::Math::XYVector support = fillFacetObservations(facet, xyl, w);
 
  LineFitPrecursor precursor = fitPrecursor(std::move(xyl), std::move(w), nSteps);
 
  // Construct and commit the fit line only when it is wanted: always for an
  // infinite maxChi2, otherwise only if the fit passes the cut. Skipping it for
  // failing facets avoids building the line and its covariance matrix. A NaN chi2
  // fails "chi2 <= maxChi2", so it is committed only in the unbounded case.
  if (std::isinf(maxChi2) or precursor.chi2 <= maxChi2) {
    const int ndf = 1;
    UncertainParameterLine2D fitLine = lineFromPrecursor(precursor, ndf);
    fitLine.passiveMoveBy(-support);
    facet.setFitLine(fitLine);
  }
  return precursor.chi2;
}

fit() [2/3]

UncertainParameterLine2D fit ( const TrackingUtilities::CDCFacet & fromFacet, const TrackingUtilities::CDCFacet & toFacet, int nSteps = 100 )

static

Fit a line the positions xyl and the weights.

Parameters

fromFacet	First facet from the pair of facets
toFacet	Second facet from the pair of facets
nSteps	Maximal number of steps to be taken in the mimisation

Definition at line 358 of file FacetFitter.cc.

{
  // Observations matrix
  Matrix<double, 6, 3> xyl = Matrix<double, 6, 3>::Zero();
 
  // Weight matrix
  Matrix<double, 6, 1> w = Matrix<double, 6, 1>::Zero();
 
  const ROOT::Math::XYVector support = fillFacetPairObservations(fromFacet, toFacet, xyl, w);
 
  UncertainParameterLine2D fitLine{ ::fit(std::move(xyl), std::move(w), nSteps) };
  fitLine.passiveMoveBy(-support);
  return fitLine;
}

fit() [3/3]

UncertainParameterLine2D fit ( TrackingUtilities::Matrix< double, 3, 3 > xyl, TrackingUtilities::Matrix< double, 3, 1 > w, int nSteps = 100 )

static

Fit a line the positions xyl and the weights.

Fits a line to a number of observations with tunable acurracy versus execution speed. Special implementations for nSteps = 0 and nSteps=1 have been integrated. High nSteps use a general minimization method.

Parameters

xyl	A matrix of drift length observations
w	An array of weights corresponding to the observations
nSteps	Maximal number of steps to be taken in the mimisation

Definition at line 392 of file FacetFitter.cc.

{
  return ::fit(std::move(xyl), std::move(w), nSteps);
}

fitChi2()

double fitChi2 ( const TrackingUtilities::CDCFacet & fromFacet, const TrackingUtilities::CDCFacet & toFacet )

static

Calculate only the chi2 of a line fitted to the hits of the two facets.

Returns the same value as fit(fromFacet, toFacet, 0).chi2() but avoids the construction of the line and its covariance matrix.

Parameters

fromFacet	First facet from the pair of facets
toFacet	Second facet from the pair of facets

Definition at line 375 of file FacetFitter.cc.

{
  // Observations matrix
  Matrix<double, 6, 3> xyl = Matrix<double, 6, 3>::Zero();
 
  // Weight matrix
  Matrix<double, 6, 1> w = Matrix<double, 6, 1>::Zero();
 
  fillFacetPairObservations(fromFacet, toFacet, xyl, w);
 
  // The chi2 is invariant against the translation by the support point
  constexpr const int nSteps = 0;
  return fitPrecursor(std::move(xyl), std::move(w), nSteps).chi2;
}

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

• tracking/trackFindingCDC/fitting/include/FacetFitter.h
• tracking/trackFindingCDC/fitting/src/FacetFitter.cc