/home/bes3soft/bes3soft/Boss/7.0.2/dist/7.0.2/Reconstruction/TrkReco/TrkReco-00-08-59-patch4-slc6tag/src/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 "CLHEP/Alist/ConstAList.h"
#include "TrkReco/TPoint2D.h"
#include "TrkReco/TLine2D.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);
}

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