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ParameterResolutions.cxx

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#include "AtlfastAlgs/ParameterResolutions.h"
#include <cmath>

namespace Atlfast {

  double ParameterResolutions::resolution(const TrackTrajectory& traj ) const{
    // resolutions are given by c0(eta) + c1(eta)/pT + c2(eta)/pT^0.5 + c3(eta)/pT^2....
    // have to interpolate eta between bin edges for coefficients
    TrackParameters track = traj.parameters();
    double eta = abs(track.eta());
    double pT = track.pT();

    vector<BinID>::const_iterator iter = m_coefficientBins.begin();
    vector<BinID>::const_iterator end = m_coefficientBins.end();
    vector<double> coefficients;
    for (;iter!=end;++iter) {
      double value = this->interpolate(eta, iter->low(), iter->high());
      coefficients.push_back(value);
    }
    return calculateResolution(pT, coefficients);
  }

  double ParameterResolutions::interpolate(double eta, double coeffLow, double coeffHigh) const {
    double slope = (coeffHigh - coeffLow) / ( m_etaHigh - m_etaLow );
    double value = ( coeffLow + slope*( eta - m_etaLow ) );
    return value;
  }
  double ParameterResolutions::calculateResolution(double pT,const vector<double>& coefficients) const{
    if (pT == 0) return 0;
    double resolution=0;
    vector<double>::const_iterator powerSeries = m_powerSeries.begin();
    vector<double>::const_iterator iter = coefficients.begin();
    vector<double>::const_iterator end = coefficients.end();
    
    for (;iter != end; ++iter)
      {
        resolution += (*iter)/( pow( pT,(*powerSeries) ) ); 
        ++powerSeries;
      }   
    return resolution;
  }

}

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