Reconstruction/MdcPatRec/TrkBase/include/TrkBase/TrkOutAvgTimeCalculator.h

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//--------------------------------------------------------------------------
// File and Version Information:
//      $Id: TrkOutAvgTimeCalculator.h,v 1.1.1.1 2005/04/21 06:01:42 zhangy Exp $
//
// Description:
//   class TrkOutAvgTimeCalculater.  A simple implementation of TrkTimeCalculator
//   that takes the weighted average of all selected hot's times assuming a
//   Gaussian error, but rejecting outliers based on their pull.
//
// Environment:
//      Software developed for the BaBar Detector at the SLAC B-Factory.
//
// Copyright Information:
//  Copyright (C) 2001  UC, San Diego
//
// Author List:
//      Gerhard Raven 7/19/01
//------------------------------------------------------------------------
 
#ifndef TRKOUTAVGTIMECALCULATOR_HH
#define TRKOUTAVGTIMECALCULATOR_HH
 
#include "TrkBase/TrkTimeCalculator.h"
#include <assert.h>
#include <math.h>
 
class TrkOutAvgTimeCalculator : public TrkTimeCalculator {
public:
  TrkOutAvgTimeCalculator( const TrkHotSelector& selector, double maxpull );
  virtual ~TrkOutAvgTimeCalculator();
  // The Function
  virtual bool trackTime( const TrkRecoTrk& trk, double& time, double& timeerr,
                          int& nHotsUsed ) const;
 
private:
  // disallow
  TrkOutAvgTimeCalculator( const TrkOutAvgTimeCalculator& );
  TrkOutAvgTimeCalculator& operator=( const TrkOutAvgTimeCalculator& );
 
  double _maxpull;
 
  class ws {
  public:
    ws( double x = 0, double w = 0 ) : _w( w ), _wx( w * x ), _n( w > 0 ? 1 : 0 ) {
      assert( !( w < 0 ) );
    }
    ws& operator+=( const ws& x ) {
      _wx += x._wx;
      _w += x._w;
      _n += x._n;
      return *this;
    }
    ws& operator-=( const ws& x ) {
      _wx -= x._wx;
      _w -= x._w;
      _n -= x._n;
      return *this;
    }
    bool   operator==( const ws& x ) const { return _w == x._w && _wx == x._wx && _n == x._n; }
    bool   isPhysical() const { return _w > 0; }
    double mean() const { return _wx / _w; }
    double sigma() const { return double( 1 ) / sqrt( _w ); }
    double pull( const ws& x ) const {
      return ( mean() - x.mean() ) / sqrt( sigma2() + x.sigma2() );
    }
    unsigned n() const { return _n; }
 
  private:
    double   sigma2() const { return double( 1 ) / _w; }
    double   _w, _wx;
    unsigned _n;
  };
};
#endif