PrincipalComponentsAlg.cxx

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#include "larreco/RecoAlg/Cluster3DAlgs/PrincipalComponentsAlg.h"

// Framework Includes
#include "art/Framework/Services/Registry/ServiceHandle.h"
#include "fhiclcpp/ParameterSet.h"
#include "messagefacility/MessageLogger/MessageLogger.h"

// LArSoft includes
#include "larcore/CoreUtils/ServiceUtil.h"
#include "larcore/Geometry/Geometry.h"
#include "larcorealg/Geometry/WireGeo.h"
#include "larcoreobj/SimpleTypesAndConstants/geo_types.h"
#include "lardataalg/DetectorInfo/DetectorPropertiesData.h"
#include "lardataobj/RecoBase/Hit.h"

// std includes
#include <functional>
#include <iostream>
#include <numeric>

// Eigen includes
#include "Eigen/Core"
#include "Eigen/Dense"
#include "Eigen/Eigenvalues"
#include "Eigen/Geometry"
#include "Eigen/Jacobi"

//------------------------------------------------------------------------------------------------------------------------------------------
// implementation follows

namespace lar_cluster3d {

  PrincipalComponentsAlg::PrincipalComponentsAlg(fhicl::ParameterSet const& pset)
  {
    m_parallel = pset.get<float>("ParallelLines", 0.00001);
    m_geometry = art::ServiceHandle<geo::Geometry const>{}.get();
  }

  struct Sort3DHitsByDocaToAxis {
    bool operator()(const reco::ClusterHit3D* left, const reco::ClusterHit3D* right) const
    {
      return left->getDocaToAxis() < right->getDocaToAxis();
    }
  };

  struct Sort3DHitsByArcLen3D {
    bool operator()(const reco::ClusterHit3D* left, const reco::ClusterHit3D* right) const
    {
      return left->getArclenToPoca() < right->getArclenToPoca();
    }
  };

  struct Sort3DHitsByAbsArcLen3D {
    bool operator()(const reco::ClusterHit3D* left, const reco::ClusterHit3D* right) const
    {
      return fabs(left->getArclenToPoca()) < fabs(right->getArclenToPoca());
    }
  };

  void PrincipalComponentsAlg::PCAAnalysis(const detinfo::DetectorPropertiesData& detProp,
                                           const reco::HitPairListPtr& hitPairVector,
                                           reco::PrincipalComponents& pca,
                                           float doca3DScl) const
  {
    // This is the controlling outside function for running
    // a Principal Components Analysis on the hits in our
    // input cluster.
    // There is a bootstrap process to be followed
    // 1) Get the initial results from all 3D hits associated
    //    with the cluster
    // 2) Refine the axis by using only the 2D hits on wires

    // Get the first axis from all 3D hits
    PCAAnalysis_3D(hitPairVector, pca);

    // Make sure first pass was good
    if (!pca.getSvdOK()) return;

    // First attempt to refine it using only 2D information
    reco::PrincipalComponents pcaLoop = pca;

    PCAAnalysis_2D(detProp, hitPairVector, pcaLoop);

    // If valid result then go to next steps
    if (pcaLoop.getSvdOK()) {
      // Let's check the angle between the original and the updated axis
      float cosAngle = pcaLoop.getEigenVectors().row(0) * pca.getEigenVectors().row(0).transpose();

      // Set the scale factor for the outlier rejection
      float sclFctr(3.);

      // If we had a significant change then let's do some outlier rejection, etc.
      if (cosAngle < 1.0) // pretty much everyone takes a turn
      {
        int maxIterations(3);
        float maxRange = 3. * sqrt(pcaLoop.getEigenValues()[1]);
        float aveDoca = pcaLoop.getAveHitDoca(); // was 0.2

        maxRange = sclFctr * 0.5 * (maxRange + aveDoca); // was std::max(maxRange, aveDoca);

        int numRejHits = PCAAnalysis_reject2DOutliers(hitPairVector, maxRange);
        int totalRejects(numRejHits);
        int maxRejects(0.4 * hitPairVector.size());

        // Try looping to see if we improve things
        while (maxIterations-- && numRejHits > 0 && totalRejects < maxRejects) {
          // Run the PCA
          PCAAnalysis_2D(detProp, hitPairVector, pcaLoop, true);

          maxRange =
            sclFctr * 0.5 * (3. * sqrt(pcaLoop.getEigenValues()[1]) + pcaLoop.getAveHitDoca());

          numRejHits = PCAAnalysis_reject2DOutliers(hitPairVector, maxRange);
        }
      }

      // Ok at this stage copy the latest results back into the cluster
      pca = pcaLoop;

      // Now we make one last pass through the 3D hits to reject outliers there
      PCAAnalysis_reject3DOutliers(hitPairVector, pca, doca3DScl * pca.getAveHitDoca());
    }
    else
      pca = pcaLoop;

    return;
  }

  void PrincipalComponentsAlg::PCAAnalysis_3D(const reco::HitPairListPtr& hitPairVector,
                                              reco::PrincipalComponents& pca,
                                              bool skeletonOnly) const
  {
    // We want to run a PCA on the input TkrVecPoints...
    // The steps are:
    // 1) do a mean normalization of the input vec points
    // 2) compute the covariance matrix
    // 3) run the SVD
    // 4) extract the eigen vectors and values
    // see what happens

    // Run through the HitPairList and get the mean position of all the hits
    Eigen::Vector3d meanPos(Eigen::Vector3d::Zero());
    double meanWeightSum(0.);
    int numPairsInt(0);

    //    const float minimumDeltaPeakSig(0.00001);
    double minimumDeltaPeakSig(0.00001);

    // Want to use the hit "chi square" to weight the hits but we need to put a lower limit on its value
    // to prevent a few hits being over counted.
    // This is a bit experimental until we can evaluate the cost (time to calculate) vs the benefit
    // (better fits)..
    std::vector<double> hitChiSquareVec;

    hitChiSquareVec.resize(hitPairVector.size());

    std::transform(hitPairVector.begin(),
                   hitPairVector.end(),
                   hitChiSquareVec.begin(),
                   [](const auto& hit) { return hit->getHitChiSquare(); });
    std::sort(hitChiSquareVec.begin(), hitChiSquareVec.end());

    size_t numToKeep = 0.8 * hitChiSquareVec.size();

    hitChiSquareVec.resize(numToKeep);

    double aveValue = std::accumulate(hitChiSquareVec.begin(), hitChiSquareVec.end(), double(0.)) /
                      double(hitChiSquareVec.size());
    double rms = std::sqrt(std::inner_product(hitChiSquareVec.begin(),
                                              hitChiSquareVec.end(),
                                              hitChiSquareVec.begin(),
                                              0.,
                                              std::plus<>(),
                                              [aveValue](const auto& left, const auto& right) {
                                                return (left - aveValue) * (right - aveValue);
                                              }) /
                           double(hitChiSquareVec.size()));

    minimumDeltaPeakSig = std::max(minimumDeltaPeakSig, aveValue - rms);

    //    std::cout << "===>> Calculating PCA, ave chiSquare: " << aveValue << ", rms: " << rms << ", cut: " << minimumDeltaPeakSig << std::endl;

    for (const auto& hit : hitPairVector) {
      if (skeletonOnly && !((hit->getStatusBits() & reco::ClusterHit3D::SKELETONHIT) ==
                            reco::ClusterHit3D::SKELETONHIT))
        continue;

      // Weight the hit by the peak time difference significance
      double weight = std::max(minimumDeltaPeakSig,
                               double(hit->getHitChiSquare())); // hit->getDeltaPeakTime());
                                                                // ///hit->getSigmaPeakTime());

      meanPos(0) += hit->getPosition()[0] * weight;
      meanPos(1) += hit->getPosition()[1] * weight;
      meanPos(2) += hit->getPosition()[2] * weight;
      numPairsInt++;

      meanWeightSum += weight;
    }

    meanPos /= meanWeightSum;

    // Define elements of our covariance matrix
    double xi2(0.);
    double xiyi(0.);
    double xizi(0.0);
    double yi2(0.0);
    double yizi(0.0);
    double zi2(0.);
    double weightSum(0.);

    // Back through the hits to build the matrix
    for (const auto& hit : hitPairVector) {
      if (skeletonOnly && !((hit->getStatusBits() & reco::ClusterHit3D::SKELETONHIT) ==
                            reco::ClusterHit3D::SKELETONHIT))
        continue;

      double weight = 1. / std::max(minimumDeltaPeakSig,
                                    double(hit->getHitChiSquare())); // hit->getDeltaPeakTime());
                                                                     // ///hit->getSigmaPeakTime());
      double x = (hit->getPosition()[0] - meanPos(0)) * weight;
      double y = (hit->getPosition()[1] - meanPos(1)) * weight;
      double z = (hit->getPosition()[2] - meanPos(2)) * weight;

      weightSum += weight * weight;

      xi2 += x * x;
      xiyi += x * y;
      xizi += x * z;
      yi2 += y * y;
      yizi += y * z;
      zi2 += z * z;
    }

    // Using Eigen package
    Eigen::Matrix3d sig;

    sig << xi2, xiyi, xizi, xiyi, yi2, yizi, xizi, yizi, zi2;

    sig *= 1. / weightSum;

    Eigen::SelfAdjointEigenSolver<Eigen::Matrix3d> eigenMat(sig);

    if (eigenMat.info() == Eigen::ComputationInfo::Success) {
      // Now copy output
      // The returned eigen values and vectors will be returned in an xyz system where x is the smallest spread,
      // y is the next smallest and z is the largest. Adopt that convention going forward
      reco::PrincipalComponents::EigenValues recobEigenVals = eigenMat.eigenvalues().cast<float>();
      reco::PrincipalComponents::EigenVectors recobEigenVecs =
        eigenMat.eigenvectors().transpose().cast<float>();

      // Check for a special case (which may have gone away with switch back to doubles for computation?)
      if (std::isnan(recobEigenVals[0])) {
        std::cout << "==> Third eigenvalue returns a nan" << std::endl;

        recobEigenVals[0] = 0.;

        // Assume the third axis is also kaput?
        recobEigenVecs.row(0) = recobEigenVecs.row(1).cross(recobEigenVecs.row(2));
      }

      // Store away
      pca = reco::PrincipalComponents(
        true, numPairsInt, recobEigenVals, recobEigenVecs, meanPos.cast<float>());
    }
    else {
      mf::LogDebug("Cluster3D") << "PCA decompose failure, numPairs = " << numPairsInt << std::endl;
      pca = reco::PrincipalComponents();
    }

    return;
  }

  void PrincipalComponentsAlg::PCAAnalysis_2D(const detinfo::DetectorPropertiesData& detProp,
                                              const reco::HitPairListPtr& hitPairVector,
                                              reco::PrincipalComponents& pca,
                                              bool updateAvePos) const
  {
    // Once an axis has been found our goal is to refine it by using only the 2D hits
    // We'll get 3D information for each of these by using the axis as a reference and use
    // the point of closest approach as the 3D position

    // Define elements of our covariance matrix
    float xi2(0.);
    float xiyi(0.);
    float xizi(0.);
    float yi2(0.);
    float yizi(0.);
    float zi2(0.);

    float aveHitDoca(0.);
    Eigen::Vector3f avePosUpdate(0., 0., 0.);
    int nHits(0);

    // Recover existing line parameters for current cluster
    const reco::PrincipalComponents& inputPca = pca;
    Eigen::Vector3f avePosition(inputPca.getAvePosition());
    Eigen::Vector3f axisDirVec(inputPca.getEigenVectors().row(0));

    // We float loop here so we can use this method for both the first time through
    // and a second time through where we re-calculate the mean position
    // So, we need to keep track of the poca which we do with a float vector
    std::vector<Eigen::Vector3f> hitPosVec;

    // Outer loop over 3D hits
    for (const auto& hit3D : hitPairVector) {
      // Inner loop over 2D hits
      for (const auto& hit : hit3D->getHits()) {
        // Step one is to set up to determine the point of closest approach of this 2D hit to
        // the cluster's current axis.
        // Get this wire's geometry object
        const geo::WireID& hitID = hit->WireID();
        const geo::WireGeo& wire_geom = m_geometry->WireIDToWireGeo(hitID);

        // From this, get the parameters of the line for the wire
        auto const wirePosArr = wire_geom.GetCenter();

        Eigen::Vector3f wireCenter(wirePosArr.X(), wirePosArr.Y(), wirePosArr.Z());
        Eigen::Vector3f wireDirVec(
          wire_geom.Direction().X(), wire_geom.Direction().Y(), wire_geom.Direction().Z());

        // Correct the wire position in x to set to correspond to the drift time
        float hitPeak(hit->getHit()->PeakTime());

        Eigen::Vector3f wirePos(
          detProp.ConvertTicksToX(hitPeak, hitID.Plane, hitID.TPC, hitID.Cryostat),
          wireCenter[1],
          wireCenter[2]);

        // Compute the wire plane normal for this view
        Eigen::Vector3f xAxis(1., 0., 0.);
        Eigen::Vector3f planeNormal =
          xAxis.cross(wireDirVec); // This gives a normal vector in +z for a Y wire

        float docaInPlane(wirePos[0] - avePosition[0]);
        float arcLenToPlane(0.);
        float cosAxisToPlaneNormal = axisDirVec.dot(planeNormal);

        Eigen::Vector3f axisPlaneIntersection = wirePos;
        Eigen::Vector3f hitPosTVec = wirePos;

        if (fabs(cosAxisToPlaneNormal) > 0.) {
          Eigen::Vector3f deltaPos = wirePos - avePosition;

          arcLenToPlane = deltaPos.dot(planeNormal) / cosAxisToPlaneNormal;
          axisPlaneIntersection = avePosition + arcLenToPlane * axisDirVec;
          docaInPlane = wirePos[0] - axisPlaneIntersection[0];

          Eigen::Vector3f axisToInter = axisPlaneIntersection - wirePos;
          float arcLenToDoca = axisToInter.dot(wireDirVec);

          hitPosTVec += arcLenToDoca * wireDirVec;
        }

        // Get a vector from the wire position to our cluster's current average position
        Eigen::Vector3f wVec = avePosition - wirePos;

        // Get the products we need to compute the arc lengths to the distance of closest approach
        float a(axisDirVec.dot(axisDirVec));
        float b(axisDirVec.dot(wireDirVec));
        float c(wireDirVec.dot(wireDirVec));
        float d(axisDirVec.dot(wVec));
        float e(wireDirVec.dot(wVec));

        float den(a * c - b * b);
        float arcLen1(0.);
        float arcLen2(0.);

        // Parallel lines is a special case
        if (fabs(den) > m_parallel) {
          arcLen1 = (b * e - c * d) / den;
          arcLen2 = (a * e - b * d) / den;
        }
        else {
          mf::LogDebug("Cluster3D") << "** Parallel lines, need a solution here" << std::endl;
          break;
        }

        // Now get the hit position we'll use for the pca analysis
        //float hitPos[]  = {wirePos[0]     + arcLen2 * wireDirVec[0],
        //                    wirePos[1]     + arcLen2 * wireDirVec[1],
        //                    wirePos[2]     + arcLen2 * wireDirVec[2]};
        //float axisPos[] = {avePosition[0] + arcLen1 * axisDirVec[0],
        //                    avePosition[1] + arcLen1 * axisDirVec[1],
        //                    avePosition[2] + arcLen1 * axisDirVec[2]};
        Eigen::Vector3f hitPos = wirePos + arcLen2 * wireDirVec;
        Eigen::Vector3f axisPos = avePosition + arcLen1 * axisDirVec;
        float deltaX = hitPos(0) - axisPos(0);
        float deltaY = hitPos(1) - axisPos(1);
        float deltaZ = hitPos(2) - axisPos(2);
        float doca2 = deltaX * deltaX + deltaY * deltaY + deltaZ * deltaZ;
        float doca = sqrt(doca2);

        docaInPlane = doca;

        aveHitDoca += fabs(docaInPlane);

        //Eigen::Vector3f deltaPos  = hitPos - hitPosTVec;
        //float   deltaDoca = doca - docaInPlane;

        //if (fabs(deltaPos[0]) > 1. || fabs(deltaPos[1]) > 1. || fabs(deltaPos[2]) > 1. || fabs(deltaDoca) > 2.)
        //{
        //    std::cout << "**************************************************************************************" << std::endl;
        //    std::cout << "Diff in doca: " << deltaPos[0] << "," << deltaPos[1] << "," << deltaPos[2] << ", deltaDoca: " << deltaDoca << std::endl;
        //    std::cout << "-- HitPosTVec: " << hitPosTVec[0] << "," << hitPosTVec[1] << "," << hitPosTVec[2] << std::endl;
        //    std::cout << "-- hitPos:     " << hitPos[0] << "," << hitPos[1] << "," << hitPos[2] << std::endl;
        //    std::cout << "-- WirePos:    " << wirePos[0] << "," << wirePos[1] << "," << wirePos[2] << std::endl;
        //}

        // Set the hit's doca and arclen
        hit->setDocaToAxis(fabs(docaInPlane));
        hit->setArcLenToPoca(arcLenToPlane);

        // If this point is considered an outlier then we skip
        // the accumulation for average position and covariance
        if (hit->getStatusBits() & 0x80) { continue; }

        //hitPosTVec = hitPos;

        avePosUpdate += hitPosTVec;

        hitPosVec.push_back(hitPosTVec);

        nHits++;
      }
    }

    // Get updated average position
    avePosUpdate /= float(nHits);

    // Get the average hit doca
    aveHitDoca /= float(nHits);

    if (updateAvePos) { avePosition = avePosUpdate; }

    // Now loop through the hits and build out the covariance matrix
    for (auto& hitPos : hitPosVec) {
      // And increment the values in the covariance matrix
      float x = hitPos[0] - avePosition[0];
      float y = hitPos[1] - avePosition[1];
      float z = hitPos[2] - avePosition[2];

      xi2 += x * x;
      xiyi += x * y;
      xizi += x * z;
      yi2 += y * y;
      yizi += y * z;
      zi2 += z * z;
    }

    // Accumulation done, now do the actual work

    // Using Eigen package
    Eigen::Matrix3f sig;

    sig << xi2, xiyi, xizi, xiyi, yi2, yizi, xizi, yizi, zi2;

    sig *= 1. / (nHits - 1);

    Eigen::SelfAdjointEigenSolver<Eigen::Matrix3f> eigenMat(sig);

    if (eigenMat.info() == Eigen::ComputationInfo::Success) {
      // Now copy output
      // The returned eigen values and vectors will be returned in an xyz system where x is the smallest spread,
      // y is the next smallest and z is the largest. Adopt that convention going forward
      reco::PrincipalComponents::EigenValues recobEigenVals = eigenMat.eigenvalues().cast<float>();
      reco::PrincipalComponents::EigenVectors recobEigenVecs =
        eigenMat.eigenvectors().transpose().cast<float>();

      // Store away
      pca = reco::PrincipalComponents(
        true, nHits, recobEigenVals, recobEigenVecs, avePosition, aveHitDoca);
    }
    else {
      mf::LogDebug("Cluster3D") << "PCA decompose failure, numPairs = " << nHits << std::endl;
      pca = reco::PrincipalComponents();
    }

    return;
  }

  void PrincipalComponentsAlg::PCAAnalysis_calc3DDocas(const reco::HitPairListPtr& hitPairVector,
                                                       const reco::PrincipalComponents& pca) const
  {
    // Our mission, should we choose to accept it, is to scan through the 2D hits and reject
    // any outliers. Basically, any hit outside a scaled range of the average doca from the
    // first pass is marked by setting the bit in the status word.

    // We'll need the current PCA axis to determine doca and arclen
    Eigen::Vector3f avePosition(
      pca.getAvePosition()[0], pca.getAvePosition()[1], pca.getAvePosition()[2]);
    Eigen::Vector3f axisDirVec(pca.getEigenVectors().row(2));

    // We want to keep track of the average
    float aveDoca3D(0.);

    // Outer loop over views
    for (const auto* clusterHit3D : hitPairVector) {
      // Always reset the existing status bit
      clusterHit3D->clearStatusBits(0x80);

      // Now we need to calculate the doca and poca...
      // Start by getting this hits position
      Eigen::Vector3f clusPos(clusterHit3D->getPosition()[0],
                              clusterHit3D->getPosition()[1],
                              clusterHit3D->getPosition()[2]);

      // Form a TVector from this to the cluster average position
      Eigen::Vector3f clusToHitVec = clusPos - avePosition;

      // With this we can get the arclength to the doca point
      float arclenToPoca = clusToHitVec.dot(axisDirVec);

      // Get the coordinates along the axis for this point
      Eigen::Vector3f docaPos = avePosition + arclenToPoca * axisDirVec;

      // Now get doca and poca
      Eigen::Vector3f docaPosToClusPos = clusPos - docaPos;
      float docaToAxis = docaPosToClusPos.norm();

      aveDoca3D += docaToAxis;

      // Ok, set the values in the hit
      clusterHit3D->setDocaToAxis(docaToAxis);
      clusterHit3D->setArclenToPoca(arclenToPoca);
    }

    // Compute the average and store
    aveDoca3D /= float(hitPairVector.size());

    pca.setAveHitDoca(aveDoca3D);

    return;
  }

  void PrincipalComponentsAlg::PCAAnalysis_calc2DDocas(const reco::Hit2DListPtr& hit2DListPtr,
                                                       const reco::PrincipalComponents& pca) const
  {
    // Our mission, should we choose to accept it, is to scan through the 2D hits and reject
    // any outliers. Basically, any hit outside a scaled range of the average doca from the
    // first pass is marked by setting the bit in the status word.

    // We'll need the current PCA axis to determine doca and arclen
    Eigen::Vector3f avePosition(
      pca.getAvePosition()[0], pca.getAvePosition()[1], pca.getAvePosition()[2]);
    Eigen::Vector3f axisDirVec(pca.getEigenVectors().row(2));

    // Recover the principle eigen value for range constraints
    float maxArcLen = 4. * sqrt(pca.getEigenValues()[0]);

    // We want to keep track of the average
    float aveHitDoca(0.);

    // Outer loop over views
    for (const auto* hit : hit2DListPtr) {
      // Step one is to set up to determine the point of closest approach of this 2D hit to
      // the cluster's current axis. We do that by finding the point of intersection of the
      // cluster's axis with a plane defined by the wire the hit is associated with.
      // Get this wire's geometry object
      const geo::WireID& hitID = hit->WireID();
      const geo::WireGeo& wire_geom = m_geometry->WireIDToWireGeo(hitID);

      // From this, get the parameters of the line for the wire
      auto const wirePosArr = wire_geom.GetCenter();

      Eigen::Vector3f wireCenter(wirePosArr.X(), wirePosArr.Y(), wirePosArr.Z());
      Eigen::Vector3f wireDirVec(
        wire_geom.Direction().X(), wire_geom.Direction().Y(), wire_geom.Direction().Z());

      // Correct the wire position in x to set to correspond to the drift time
      Eigen::Vector3f wirePos(hit->getXPosition(), wireCenter[1], wireCenter[2]);

      // Compute the wire plane normal for this view
      Eigen::Vector3f xAxis(1., 0., 0.);
      Eigen::Vector3f planeNormal =
        xAxis.cross(wireDirVec); // This gives a normal vector in +z for a Y wire

      float arcLenToPlane(0.);
      float docaInPlane(wirePos[0] - avePosition[0]);
      float cosAxisToPlaneNormal = axisDirVec.dot(planeNormal);

      Eigen::Vector3f axisPlaneIntersection = wirePos;

      // If current cluster axis is not parallel to wire plane then find intersection point
      if (fabs(cosAxisToPlaneNormal) > 0.) {
        Eigen::Vector3f deltaPos = wirePos - avePosition;

        arcLenToPlane =
          std::min(float(deltaPos.dot(planeNormal) / cosAxisToPlaneNormal), maxArcLen);
        axisPlaneIntersection = avePosition + arcLenToPlane * axisDirVec;

        Eigen::Vector3f axisToInter = axisPlaneIntersection - wirePos;
        float arcLenToDoca = axisToInter.dot(wireDirVec);

        // If the arc length along the wire to the poca is outside the TPC then reset
        if (fabs(arcLenToDoca) > wire_geom.HalfL()) arcLenToDoca = wire_geom.HalfL();

        // If we were successful in getting to the wire plane then the doca is simply the
        // difference in x coordinates... but we hvae to worry about the special cases so
        // we calculate a 3D doca based on arclengths above...
        Eigen::Vector3f docaVec = axisPlaneIntersection - (wirePos + arcLenToDoca * wireDirVec);
        docaInPlane = docaVec.norm();
      }

      aveHitDoca += fabs(docaInPlane);

      // Set the hit's doca and arclen
      hit->setDocaToAxis(fabs(docaInPlane));
      hit->setArcLenToPoca(arcLenToPlane);
    }

    // Compute the average and store
    aveHitDoca /= float(hit2DListPtr.size());

    pca.setAveHitDoca(aveHitDoca);

    return;
  }

  int PrincipalComponentsAlg::PCAAnalysis_reject2DOutliers(
    const reco::HitPairListPtr& hitPairVector,
    float maxDocaAllowed) const
  {
    // Our mission, should we choose to accept it, is to scan through the 2D hits and reject
    // any outliers. Basically, any hit outside a scaled range of the average doca from the
    // first pass is marked by setting the bit in the status word.

    // First get the average doca scaled by some appropriate factor
    int numRejHits(0);

    // Outer loop over views
    for (const auto& hit3D : hitPairVector) {
      // Inner loop over hits in this view
      for (const auto& hit : hit3D->getHits()) {
        // Always reset the existing status bit
        hit->clearStatusBits(0x80);

        if (hit->getDocaToAxis() > maxDocaAllowed) {
          hit->setStatusBit(0x80);
          numRejHits++;
        }
      }
    }

    return numRejHits;
  }

  int PrincipalComponentsAlg::PCAAnalysis_reject3DOutliers(
    const reco::HitPairListPtr& hitPairVector,
    const reco::PrincipalComponents& pca,
    float maxDocaAllowed) const
  {
    // Our mission, should we choose to accept it, is to scan through the 2D hits and reject
    // any outliers. Basically, any hit outside a scaled range of the average doca from the
    // first pass is marked by setting the bit in the status word.

    // First get the average doca scaled by some appropriate factor
    int numRejHits(0);

    // We'll need the current PCA axis to determine doca and arclen
    Eigen::Vector3f avePosition(
      pca.getAvePosition()[0], pca.getAvePosition()[1], pca.getAvePosition()[2]);
    Eigen::Vector3f axisDirVec(pca.getEigenVectors().row(2));

    // Outer loop over views
    for (const auto* clusterHit3D : hitPairVector) {
      // Always reset the existing status bit
      clusterHit3D->clearStatusBits(0x80);

      // Now we need to calculate the doca and poca...
      // Start by getting this hits position
      Eigen::Vector3f clusPos(clusterHit3D->getPosition()[0],
                              clusterHit3D->getPosition()[1],
                              clusterHit3D->getPosition()[2]);

      // Form a TVector from this to the cluster average position
      Eigen::Vector3f clusToHitVec = clusPos - avePosition;

      // With this we can get the arclength to the doca point
      float arclenToPoca = clusToHitVec.dot(axisDirVec);

      // Get the coordinates along the axis for this point
      Eigen::Vector3f docaPos = avePosition + arclenToPoca * axisDirVec;

      // Now get doca and poca
      Eigen::Vector3f docaPosToClusPos = clusPos - docaPos;
      float docaToAxis = docaPosToClusPos.norm();

      // Ok, set the values in the hit
      clusterHit3D->setDocaToAxis(docaToAxis);
      clusterHit3D->setArclenToPoca(arclenToPoca);

      // Check to see if this is a keeper
      if (clusterHit3D->getDocaToAxis() > maxDocaAllowed) {
        clusterHit3D->setStatusBit(0x80);
        numRejHits++;
      }
    }

    return numRejHits;
  }

} // namespace lar_cluster3d