/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_7/src/RecoTauTag/HLTProducers/src/L2TauSimpleClustering.cc

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#include "RecoTauTag/HLTProducers/interface/L2TauSimpleClustering.h"
#include "Math/GenVector/VectorUtil.h"


L2TauSimpleClustering::L2TauSimpleClustering()
{
  m_clusterRadius=0.08;
}

L2TauSimpleClustering::L2TauSimpleClustering(double radius)
{
  m_clusterRadius=radius;
}

L2TauSimpleClustering::~L2TauSimpleClustering()
{}


math::PtEtaPhiELorentzVectorCollection 
L2TauSimpleClustering::clusterize(const math::PtEtaPhiELorentzVectorCollection& myRecHits)
{

  math::PtEtaPhiELorentzVectorCollection m_clusters;

   //If we have Hits do Clustering
   if(myRecHits.size()>0)
     {
       //Create the first Cluster by maximum Crystal
       m_clusters.push_back(myRecHits[0]);

       //Loop on The Clusters if there are at least two hits
       if(myRecHits.size()>=2)
       for(math::PtEtaPhiELorentzVectorCollection::const_iterator h = myRecHits.begin()+1;h!=myRecHits.end();++h)
       {
          //These vars are used to find the nearest clusters to this hits
          double dR_min=100;  
          int ptr=0;
          int ptr_min=-1;
         
          for(math::PtEtaPhiELorentzVectorCollection::iterator j=m_clusters.begin()+1;j!=m_clusters.end();j++)
          {
             if(ROOT::Math::VectorUtil::DeltaR(*h,*j)<m_clusterRadius)
                {
                  if(ROOT::Math::VectorUtil::DeltaR(*h,*j)<dR_min)
                    {
                      dR_min=ROOT::Math::VectorUtil::DeltaR(*h,*j);
                      ptr_min=ptr;
                    }
                }
                  ptr++;
          }
             
          //If it does not belong to cluster add a new one else add the Crystal to the Cluster
          if(ptr_min==-1)
            m_clusters.push_back(*h);
          else
            m_clusters[ptr_min]+=*h;
       }
              
     }
   return m_clusters;
}