TLine2D.cxx

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//-----------------------------------------------------------------------------
// $Id: TLine2D.cxx,v 1.5 2010/03/31 09:58:59 liucy Exp $
//-----------------------------------------------------------------------------
// Filename : TLine2D.cc
// Section  : Tracking
// Owner    : Yoshi Iwasaki
// Email    : yoshihito.iwasaki@kek.jp
//-----------------------------------------------------------------------------
// Description : A class to represent a line in 2D.
//               See http://bsunsrv1.kek.jp/~yiwasaki/tracking/
//-----------------------------------------------------------------------------
// $Log: TLine2D.cxx,v $
// Revision 1.5  2010/03/31 09:58:59  liucy
// CLHEP based on 05.17
//
// Revision 1.2  2005/09/09 07:47:07  zangsl
// 20050909 boss4.2 freeze
//
// Revision 1.1  1999/11/19 09:13:08  yiwasaki
// Trasan 1.65d : new conf. finder updates, no change in default conf. finder
//
//
//-----------------------------------------------------------------------------
 
#define TLINE2D_INLINE_DEFINE_HERE
// #define HEP_SHORT_NAMES
#include "TrkReco/TLine2D.h"
#include "TrkReco/TPoint2D.h"
 
TLine2D::TLine2D() : _slope( 1 ), _yOffset( 0 ), _det( 0 ), _list( 0 ) {}
 
TLine2D::TLine2D( double a, double b ) : _slope( a ), _yOffset( b ), _det( 0 ), _list( 0 ) {}
 
TLine2D::TLine2D( const AList<TPoint2D>& a ) : _slope( 1 ), _yOffset( 0 ), _det( 0 ) {
  _list = new CAList<TPoint2D>();
  _list->append( a );
}
 
TLine2D::~TLine2D() {
  if ( _list ) delete _list;
}
 
void TLine2D::append( const TPoint2D& a ) {
  if ( !_list ) _list = new CAList<TPoint2D>();
  _list->append( a );
}
 
void TLine2D::remove( const TPoint2D& a ) {
  if ( !_list ) return;
  _list->remove( a );
}
 
const CAList<TPoint2D>& TLine2D::list( void ) const {
  if ( !_list ) _list = new CAList<TPoint2D>();
  return *_list;
}
 
int TLine2D::fit( void ) {
  if ( !_list ) return -1;
 
  unsigned n = _list->length();
  if ( !n ) return -1;
 
  if ( n == 2 )
  {
    double x0 = ( *_list )[0]->x();
    double y0 = ( *_list )[0]->y();
    double x1 = ( *_list )[1]->x();
    double y1 = ( *_list )[1]->y();
    if ( x0 == x1 ) return -2;
    _slope   = ( y0 - y1 ) / ( x0 - x1 );
    _yOffset = -_slope * x1 + y1;
 
    return 0;
  }
 
  double sum  = double( n );
  double sumX = 0., sumY = 0., sumX2 = 0., sumXY = 0., sumY2 = 0.;
  for ( unsigned i = 0; i < n; i++ )
  {
    const TPoint2D& p = *( *_list )[i];
    double          x = p.x();
    double          y = p.y();
    sumX += x;
    sumY += y;
    sumX2 += x * x;
    sumXY += x * y;
    sumY2 += y * y;
  }
 
  _det = sum * sumX2 - sumX * sumX;
  if ( _det == 0. ) return -3;
 
  _slope   = ( sumXY * sum - sumX * sumY ) / _det;
  _yOffset = ( sumX2 * sumY - sumX * sumXY ) / _det;
 
  return 0;
}
 
double TLine2D::distance( const TPoint2D& p ) const {
  double ydif  = p.y() - _yOffset;
  double vmag  = sqrt( 1. + _slope * _slope );
  double dot   = ( p.x() + ydif * _slope ) / vmag;
  double xmag2 = p.x() * p.x() + ydif * ydif;
  return sqrt( xmag2 - dot * dot );
}