/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_5/src/RecoVertex/GaussianSumVertexFit/src/VertexGaussianStateConversions.cc

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#include "RecoVertex/GaussianSumVertexFit/interface/VertexGaussianStateConversions.h"

#include "RecoVertex/GaussianSumVertexFit/interface/BasicMultiVertexState.h"
#include "TrackingTools/GsfTools/interface/SingleGaussianState.h"
#include "boost/shared_ptr.hpp"

namespace GaussianStateConversions {

  MultiGaussianState<3> multiGaussianStateFromVertex (const VertexState aState)
  {
    typedef boost::shared_ptr< SingleGaussianState<3> > SingleStatePtr;
    const std::vector<VertexState> components = aState.components();
    MultiGaussianState<3>::SingleStateContainer singleStates;
    singleStates.reserve(components.size());
    for ( std::vector<VertexState>::const_iterator ic=components.begin();
          ic!=components.end(); ic ++ ) {
      if ( ic->isValid() ) {
        GlobalPoint pos(ic->position());
        AlgebraicVector3 parameters;
        parameters(0) = pos.x(); parameters(1) = pos.y(); parameters(2) = pos.z();
        SingleStatePtr sgs(new SingleGaussianState<3>(parameters,
                                                         ic->error().matrix_new(),
                                                         ic->weightInMixture()));
        singleStates.push_back(sgs);
      }
    }
    return MultiGaussianState<3>(singleStates);
  }

  VertexState vertexFromMultiGaussianState (const MultiGaussianState<3>& multiState)
  {
    if ( multiState.components().empty() )  return VertexState();

    const MultiGaussianState<3>::SingleStateContainer& singleStates = 
      multiState.components();
    std::vector<VertexState> components;
    components.reserve(singleStates.size());
    for ( MultiGaussianState<3>::SingleStateContainer::const_iterator ic=singleStates.begin();
          ic!=singleStates.end(); ic++ ) {
      const AlgebraicVector3& par = (**ic).mean();
      GlobalPoint position(par(0),par(1),par(2));
      const AlgebraicSymMatrix33& cov = (**ic).covariance();
      GlobalError error(cov(0,0),cov(1,0),cov(2,0),cov(1,1),cov(2,1),cov(2,2));
      components.push_back(VertexState(position,error,(**ic).weight()));
    }
    return VertexState(new BasicMultiVertexState(components));
  }
}