MRMTransitionGroupPicker.h

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// --------------------------------------------------------------------------
//                   OpenMS -- Open-Source Mass Spectrometry
// --------------------------------------------------------------------------
// Copyright The OpenMS Team -- Eberhard Karls University Tuebingen,
// ETH Zurich, and Freie Universitaet Berlin 2002-2020.
//
// This software is released under a three-clause BSD license:
//  * Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//  * Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
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//    may be used to endorse or promote products derived from this software
//    without specific prior written permission.
// For a full list of authors, refer to the file AUTHORS.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
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// --------------------------------------------------------------------------
// $Maintainer: Hannes Roest $
// $Authors: Hannes Roest $
// --------------------------------------------------------------------------
 
#pragma once
 
#include <OpenMS/KERNEL/MRMTransitionGroup.h>
#include <OpenMS/KERNEL/MRMFeature.h>
#include <OpenMS/KERNEL/MSSpectrum.h>
#include <OpenMS/KERNEL/MSChromatogram.h>
#include <OpenMS/KERNEL/ChromatogramPeak.h>
#include <OpenMS/ANALYSIS/OPENSWATH/PeakIntegrator.h>
 
#include <OpenMS/ANALYSIS/OPENSWATH/PeakPickerMRM.h>
#include <OpenMS/FILTERING/TRANSFORMERS/LinearResamplerAlign.h>
 
#include <OpenMS/DATASTRUCTURES/DefaultParamHandler.h>
#include <OpenMS/CONCEPT/LogStream.h>
 
// Cross-correlation
#include <OpenMS/OPENSWATHALGO/ALGO/Scoring.h>
#include <OpenMS/OPENSWATHALGO/ALGO/StatsHelpers.h>
 
#include <numeric>
 
//#define DEBUG_TRANSITIONGROUPPICKER
 
namespace OpenMS
{
 
  class OPENMS_DLLAPI MRMTransitionGroupPicker :
    public DefaultParamHandler
  {
 
public:
 
    MRMTransitionGroupPicker();
 
    ~MRMTransitionGroupPicker() override;
 
    template <typename SpectrumT, typename TransitionT>
    void pickTransitionGroup(MRMTransitionGroup<SpectrumT, TransitionT>& transition_group)
    {
      OPENMS_PRECONDITION(transition_group.isInternallyConsistent(), "Consistent state required")
      OPENMS_PRECONDITION(transition_group.chromatogramIdsMatch(), "Chromatogram native IDs need to match keys in transition group")
 
      std::vector<MSChromatogram > picked_chroms;
      std::vector<MSChromatogram > smoothed_chroms;
 
      // Pick fragment ion chromatograms
      for (Size k = 0; k < transition_group.getChromatograms().size(); k++)
      {
        MSChromatogram& chromatogram = transition_group.getChromatograms()[k];
        String native_id = chromatogram.getNativeID();
 
        // only pick detecting transitions (skip all others)
        if (transition_group.getTransitions().size() > 0 && 
            transition_group.hasTransition(native_id)  && 
            !transition_group.getTransition(native_id).isDetectingTransition() )
        {
          continue;
        }
 
        MSChromatogram picked_chrom, smoothed_chrom;
        smoothed_chrom.setNativeID(native_id);
        picker_.pickChromatogram(chromatogram, picked_chrom, smoothed_chrom);
        picked_chrom.sortByIntensity();
        picked_chroms.push_back(std::move(picked_chrom));
        smoothed_chroms.push_back(std::move(smoothed_chrom));
      }
 
      // Pick precursor chromatograms
      if (use_precursors_)
      {
        for (Size k = 0; k < transition_group.getPrecursorChromatograms().size(); k++)
        {
          SpectrumT picked_chrom, smoothed_chrom;
          SpectrumT& chromatogram = transition_group.getPrecursorChromatograms()[k];
 
          picker_.pickChromatogram(chromatogram, picked_chrom, smoothed_chrom);
          picked_chrom.sortByIntensity();
          picked_chroms.push_back(picked_chrom);
          smoothed_chroms.push_back(smoothed_chrom);
        }
      }
 
      // Find features (peak groups) in this group of transitions.
      // While there are still peaks left, one will be picked and used to create
      // a feature. Whenever we run out of peaks, we will get -1 back as index
      // and terminate.
      int chr_idx, peak_idx, cnt = 0;
      std::vector<MRMFeature> features;
      while (true)
      {
        chr_idx = -1; peak_idx = -1;
 
        if (boundary_selection_method_ == "largest")
        {
          findLargestPeak(picked_chroms, chr_idx, peak_idx);
        }
        else if (boundary_selection_method_ == "widest")
        {
          findWidestPeakIndices(picked_chroms, chr_idx, peak_idx);
        }
 
        if (chr_idx == -1 && peak_idx == -1)
        {
          OPENMS_LOG_DEBUG << "**** MRMTransitionGroupPicker : no more peaks left" << picked_chroms.size() << std::endl;
          break;
        }
 
        // Compute a feature from the individual chromatograms and add non-zero features
        MRMFeature mrm_feature = createMRMFeature(transition_group, picked_chroms, smoothed_chroms, chr_idx, peak_idx);
        double total_xic = 0;
        double intensity = mrm_feature.getIntensity();
        if (intensity > 0)
        {
          total_xic = mrm_feature.getMetaValue("total_xic");
          features.push_back(std::move(mrm_feature));
          cnt++;
        }
 
        if (stop_after_feature_ > 0 && cnt > stop_after_feature_) {break;}
        if (intensity > 0 && intensity / total_xic < stop_after_intensity_ratio_)
        {
          break;
        }
      }
 
      // Check for completely overlapping features
      for (Size i = 0; i < features.size(); i++)
      {
        MRMFeature& mrm_feature = features[i];
        bool skip = false;
        for (Size j = 0; j < i; j++)
        {
          if ((double)mrm_feature.getMetaValue("leftWidth") >=  (double)features[j].getMetaValue("leftWidth") && 
              (double)mrm_feature.getMetaValue("rightWidth") <= (double)features[j].getMetaValue("rightWidth") )
          { skip = true; }
        }
        if (mrm_feature.getIntensity() > 0 && !skip)
        {
          transition_group.addFeature(mrm_feature);
        }
      }
 
    }
 
    template <typename SpectrumT, typename TransitionT>
    MRMFeature createMRMFeature(const MRMTransitionGroup<SpectrumT, TransitionT>& transition_group,
                                std::vector<SpectrumT>& picked_chroms,
                                const std::vector<SpectrumT>& smoothed_chroms,
                                const int chr_idx,
                                const int peak_idx)
    {
      OPENMS_PRECONDITION(transition_group.isInternallyConsistent(), "Consistent state required")
      OPENMS_PRECONDITION(transition_group.chromatogramIdsMatch(), "Chromatogram native IDs need to match keys in transition group")
 
      MRMFeature mrmFeature;
      mrmFeature.setIntensity(0.0);
      double best_left = picked_chroms[chr_idx].getFloatDataArrays()[PeakPickerMRM::IDX_LEFTBORDER][peak_idx];
      double best_right = picked_chroms[chr_idx].getFloatDataArrays()[PeakPickerMRM::IDX_RIGHTBORDER][peak_idx];
      double peak_apex = picked_chroms[chr_idx][peak_idx].getRT();
      OPENMS_LOG_DEBUG << "**** Creating MRMFeature for peak " << chr_idx << " " << peak_idx << " " <<
        picked_chroms[chr_idx][peak_idx] << " with borders " << best_left << " " <<
        best_right << " (" << best_right - best_left << ")" << std::endl;
 
      if (use_consensus_ && recalculate_peaks_)
      {
        // This may change best_left / best_right
        recalculatePeakBorders_(picked_chroms, best_left, best_right, recalculate_peaks_max_z_);
        if (peak_apex < best_left || peak_apex > best_right)
        {
          // apex fell out of range, lets correct it
          peak_apex = (best_left + best_right) / 2.0;
        }
      }
 
      std::vector< double > left_edges;
      std::vector< double > right_edges;
      double min_left = best_left;
      double max_right = best_right;
      if (use_consensus_)
      {
        // Remove other, overlapping, picked peaks (in this and other
        // chromatograms) and then ensure that at least one peak is set to zero
        // (the currently best peak).
        remove_overlapping_features(picked_chroms, best_left, best_right);
      }
      else
      {
        pickApex(picked_chroms, best_left, best_right, peak_apex,
                 min_left, max_right, left_edges, right_edges);
 
      } // end !use_consensus_
      picked_chroms[chr_idx][peak_idx].setIntensity(0.0); // ensure that we set at least one peak to zero
 
      // Check for minimal peak width -> return empty feature (Intensity zero)
      if (use_consensus_)
      {
        if (min_peak_width_ > 0.0 && std::fabs(best_right - best_left) < min_peak_width_) 
        {
          return mrmFeature;
        }
 
        if (compute_peak_quality_)
        {
          String outlier = "none";
          double qual = computeQuality_(transition_group, picked_chroms, chr_idx, best_left, best_right, outlier);
          if (qual < min_qual_) 
          {
            return mrmFeature;
          }
          mrmFeature.setMetaValue("potentialOutlier", outlier);
          mrmFeature.setMetaValue("initialPeakQuality", qual);
          mrmFeature.setOverallQuality(qual);
        }
      }
 
      // Prepare linear resampling of all the chromatograms, here creating the
      // empty master_peak_container with the same RT (m/z) values as the
      // reference chromatogram. We use the overall minimal left boundary and
      // maximal right boundary to prepare the container.
      SpectrumT master_peak_container;
      const SpectrumT& ref_chromatogram = selectChromHelper_(transition_group, picked_chroms[chr_idx].getNativeID());
      prepareMasterContainer_(ref_chromatogram, master_peak_container, min_left, max_right);
 
      // Iterate over initial transitions / chromatograms (note that we may
      // have a different number of picked chromatograms than total transitions
      // as not all are detecting transitions).
      double total_intensity = 0; double total_peak_apices = 0; double total_xic = 0; double total_mi = 0;
      pickFragmentChromatograms(transition_group, picked_chroms, mrmFeature, smoothed_chroms,
                                best_left, best_right, use_consensus_,
                                total_intensity, total_xic, total_mi, total_peak_apices,
                                master_peak_container, left_edges, right_edges,
                                chr_idx, peak_idx);
 
      // Also pick the precursor chromatogram(s); note total_xic is not
      // extracted here, only for fragment traces
      pickPrecursorChromatograms(transition_group,
                                picked_chroms, mrmFeature, smoothed_chroms,
                                best_left, best_right, use_consensus_,
                                total_intensity, master_peak_container, left_edges, right_edges,
                                chr_idx, peak_idx);
 
      mrmFeature.setRT(peak_apex);
      mrmFeature.setIntensity(total_intensity);
      mrmFeature.setMetaValue("PeptideRef", transition_group.getTransitionGroupID());
      mrmFeature.setMetaValue("leftWidth", best_left);
      mrmFeature.setMetaValue("rightWidth", best_right);
      mrmFeature.setMetaValue("total_xic", total_xic);
      if (compute_total_mi_)
      {
        mrmFeature.setMetaValue("total_mi", total_mi);
      }
      mrmFeature.setMetaValue("peak_apices_sum", total_peak_apices);
 
      mrmFeature.ensureUniqueId();
      return mrmFeature;
    }
 
    template <typename SpectrumT>
    void pickApex(std::vector<SpectrumT>& picked_chroms,
                  const double best_left, const double best_right, const double peak_apex,
                  double &min_left, double &max_right, 
                  std::vector< double > & left_edges, std::vector< double > & right_edges)
    {
      for (Size k = 0; k < picked_chroms.size(); k++)
      {
        double peak_apex_dist_min = std::numeric_limits<double>::max();
        int min_dist = -1;
        for (Size i = 0; i < picked_chroms[k].size(); i++)
        {
          PeakIntegrator::PeakArea pa_tmp = pi_.integratePeak(  // get the peak apex
              picked_chroms[k],
              picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_LEFTBORDER][i], 
              picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_RIGHTBORDER][i]); 
          if (pa_tmp.apex_pos > 0.0 && std::fabs(pa_tmp.apex_pos - peak_apex) < peak_apex_dist_min)
          { // update best candidate
            peak_apex_dist_min = std::fabs(pa_tmp.apex_pos - peak_apex);
            min_dist = (int)i;
          }
        }
 
        // Select master peak boundaries, or in the case we found at least one peak, the local peak boundaries 
        double l = best_left;
        double r = best_right;
        if (min_dist >= 0)
        {
          l = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_LEFTBORDER][min_dist];
          r = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_RIGHTBORDER][min_dist];
          picked_chroms[k][min_dist].setIntensity(0.0); // only remove one peak per transition
        }
 
        left_edges.push_back(l);
        right_edges.push_back(r);
        // ensure we remember the overall maxima / minima
        if (l < min_left) {min_left = l;}
        if (r > max_right) {max_right = r;}
      }
    }
 
    template <typename SpectrumT, typename TransitionT>
    void pickFragmentChromatograms(const MRMTransitionGroup<SpectrumT, TransitionT>& transition_group,
                                    const std::vector<SpectrumT>& picked_chroms,
                                    MRMFeature& mrmFeature,
                                    const std::vector<SpectrumT>& smoothed_chroms,
                                    const double best_left, const double best_right,
                                    const bool use_consensus_,
                                    double & total_intensity,
                                    double & total_xic,
                                    double & total_mi,
                                    double & total_peak_apices,
                                    const SpectrumT & master_peak_container,
                                    const std::vector< double > & left_edges,
                                    const std::vector< double > & right_edges,
                                    const int chr_idx,
                                    const int peak_idx)
    {
      for (Size k = 0; k < transition_group.getTransitions().size(); k++)
      {
 
        double local_left = best_left;
        double local_right = best_right;
        if (!use_consensus_)
        {
          // We cannot have any non-detecting transitions (otherwise we have
          // too few left / right edges) as we skipped those when doing peak
          // picking and smoothing.
          if (!transition_group.getTransitions()[k].isDetectingTransition())
          {
            throw Exception::IllegalArgument(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION,
                "When using non-censensus peak picker, all transitions need to be detecting transitions.");
          }
          local_left = left_edges[k];
          local_right = right_edges[k];
        }
 
        const SpectrumT& chromatogram = selectChromHelper_(transition_group, transition_group.getTransitions()[k].getNativeID()); 
        if (transition_group.getTransitions()[k].isDetectingTransition())
        {
          for (typename SpectrumT::const_iterator it = chromatogram.begin(); it != chromatogram.end(); it++)
          {
            total_xic += it->getIntensity();
          }
        }
 
        // Compute total intensity on transition-level
        double transition_total_xic = 0; 
 
        for (typename SpectrumT::const_iterator it = chromatogram.begin(); it != chromatogram.end(); it++)
        {
          transition_total_xic += it->getIntensity();
        }
 
        // Compute total mutual information on transition-level.
        double transition_total_mi = 0;
        if (compute_total_mi_)
        {
          std::vector<double> chrom_vect_id, chrom_vect_det;
          for (typename SpectrumT::const_iterator it = chromatogram.begin(); it != chromatogram.end(); it++)
          {
            chrom_vect_id.push_back(it->getIntensity());
          }
 
          // compute baseline mutual information
          int transition_total_mi_norm = 0;
          for (Size m = 0; m < transition_group.getTransitions().size(); m++)
          {
            if (transition_group.getTransitions()[m].isDetectingTransition())
            {
              const SpectrumT& chromatogram_det = selectChromHelper_(transition_group, transition_group.getTransitions()[m].getNativeID());
              chrom_vect_det.clear();
              for (typename SpectrumT::const_iterator it = chromatogram_det.begin(); it != chromatogram_det.end(); it++)
              {
                chrom_vect_det.push_back(it->getIntensity());
              }
              transition_total_mi += OpenSwath::Scoring::rankedMutualInformation(chrom_vect_det, chrom_vect_id);
              transition_total_mi_norm++;
            }
          }
          if (transition_total_mi_norm > 0) { transition_total_mi /= transition_total_mi_norm; }
 
          if (transition_group.getTransitions()[k].isDetectingTransition())
          {
            // sum up all transition-level total MI and divide by the number of detection transitions to have peak group level total MI
            total_mi += transition_total_mi / transition_total_mi_norm;
          }
        }
 
        SpectrumT used_chromatogram;
        // resample the current chromatogram
        if (peak_integration_ == "original")
        {
          used_chromatogram = resampleChromatogram_(chromatogram, master_peak_container, local_left, local_right);
        }
        else if (peak_integration_ == "smoothed")
        {
          if (smoothed_chroms.size() <= k) 
          {
            throw Exception::IllegalArgument(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION,
                                             "Tried to calculate peak area and height without any smoothed chromatograms");
          }
          used_chromatogram = resampleChromatogram_(smoothed_chroms[k], master_peak_container, local_left, local_right);
        }
        else
        {
          throw Exception::IllegalArgument(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION,
            String("Peak integration chromatogram ") + peak_integration_ + " is not a valid method for MRMTransitionGroupPicker");
        } 
 
        Feature f;
        double quality = 0;
        f.setQuality(0, quality);
        f.setOverallQuality(quality);
 
        PeakIntegrator::PeakArea pa = pi_.integratePeak(used_chromatogram, local_left, local_right);
        double peak_integral = pa.area;
        double peak_apex_int = pa.height;
        f.setMetaValue("peak_apex_position", pa.apex_pos);
        if (background_subtraction_ != "none")
        {
          double background{0};
          double avg_noise_level{0};
          if (background_subtraction_ == "original")
          {
            const double intensity_left = chromatogram.PosBegin(local_left)->getIntensity();
            const double intensity_right = (chromatogram.PosEnd(local_right) - 1)->getIntensity();
            const UInt n_points = std::distance(chromatogram.PosBegin(local_left), chromatogram.PosEnd(local_right));
            avg_noise_level = (intensity_right + intensity_left) / 2;
            background = avg_noise_level * n_points;
          }
          else if (background_subtraction_ == "exact")
          {
            PeakIntegrator::PeakBackground pb = pi_.estimateBackground(used_chromatogram, local_left, local_right, pa.apex_pos);
            background = pb.area;
            avg_noise_level = pb.height;
          }
          peak_integral -= background;
          peak_apex_int -= avg_noise_level;
          if (peak_integral < 0) {peak_integral = 0;}
          if (peak_apex_int < 0) {peak_apex_int = 0;}
 
          f.setMetaValue("area_background_level", background);
          f.setMetaValue("noise_background_level", avg_noise_level);
        } // end background
 
        f.setRT(picked_chroms[chr_idx][peak_idx].getMZ());
        f.setIntensity(peak_integral);
        ConvexHull2D hull;
        hull.setHullPoints(pa.hull_points);
        f.getConvexHulls().push_back(hull);
 
        f.setMZ(chromatogram.getProduct().getMZ());
        mrmFeature.setMZ(chromatogram.getPrecursor().getMZ());
 
        if (chromatogram.metaValueExists("product_mz")) // legacy code (ensures that old tests still work)
        {
          f.setMetaValue("MZ", chromatogram.getMetaValue("product_mz"));
          f.setMZ(chromatogram.getMetaValue("product_mz"));
        }
 
        f.setMetaValue("native_id", chromatogram.getNativeID());
        f.setMetaValue("peak_apex_int", peak_apex_int);
        f.setMetaValue("total_xic", transition_total_xic);
        if (compute_total_mi_)
        {
          f.setMetaValue("total_mi", transition_total_mi);
        }
 
        if (transition_group.getTransitions()[k].isQuantifyingTransition())
        {
          total_intensity += peak_integral;
          total_peak_apices += peak_apex_int;
        }
 
        // for backwards compatibility with TOPP tests
        // Calculate peak shape metrics that will be used for later QC
        PeakIntegrator::PeakShapeMetrics psm = pi_.calculatePeakShapeMetrics(used_chromatogram, local_left, local_right, peak_apex_int, pa.apex_pos);
        f.setMetaValue("width_at_50", psm.width_at_50);
        if (compute_peak_shape_metrics_)
        {
          f.setMetaValue("width_at_5", psm.width_at_5);
          f.setMetaValue("width_at_10", psm.width_at_10);
          f.setMetaValue("start_position_at_5", psm.start_position_at_5);
          f.setMetaValue("start_position_at_10", psm.start_position_at_10);
          f.setMetaValue("start_position_at_50", psm.start_position_at_50);
          f.setMetaValue("end_position_at_5", psm.end_position_at_5);
          f.setMetaValue("end_position_at_10", psm.end_position_at_10);
          f.setMetaValue("end_position_at_50", psm.end_position_at_50);
          f.setMetaValue("total_width", psm.total_width);
          f.setMetaValue("tailing_factor", psm.tailing_factor);
          f.setMetaValue("asymmetry_factor", psm.asymmetry_factor);
          f.setMetaValue("slope_of_baseline", psm.slope_of_baseline);
          f.setMetaValue("baseline_delta_2_height", psm.baseline_delta_2_height);
          f.setMetaValue("points_across_baseline", psm.points_across_baseline);
          f.setMetaValue("points_across_half_height", psm.points_across_half_height);
        }
 
        mrmFeature.addFeature(f, chromatogram.getNativeID()); //map index and feature
      }
    }
 
    template <typename SpectrumT, typename TransitionT>
    void pickPrecursorChromatograms(const MRMTransitionGroup<SpectrumT, TransitionT>& transition_group,
                                    const std::vector<SpectrumT>& picked_chroms,
                                    MRMFeature& mrmFeature,
                                    const std::vector<SpectrumT>& smoothed_chroms,
                                    const double best_left, const double best_right,
                                    const bool use_consensus_,
                                    double & total_intensity,
                                    const SpectrumT & master_peak_container,
                                    const std::vector< double > & left_edges,
                                    const std::vector< double > & right_edges,
                                    const int chr_idx,
                                    const int peak_idx)
    {
      for (Size k = 0; k < transition_group.getPrecursorChromatograms().size(); k++)
      {
        const SpectrumT& chromatogram = transition_group.getPrecursorChromatograms()[k];
 
        // Identify precursor index
        // note: this is only valid if all transitions are detecting transitions
        Size prec_idx = transition_group.getChromatograms().size() + k;
 
        double local_left = best_left;
        double local_right = best_right;
        if (!use_consensus_ && right_edges.size() > prec_idx && left_edges.size() > prec_idx)
        {
          local_left = left_edges[prec_idx];
          local_right = right_edges[prec_idx];
        }
 
        SpectrumT used_chromatogram;
        // resample the current chromatogram
        if (peak_integration_ == "original")
        {
          used_chromatogram = resampleChromatogram_(chromatogram, master_peak_container, local_left, local_right);
          // const SpectrumT& used_chromatogram = chromatogram; // instead of resampling
        }
        else if (peak_integration_ == "smoothed" && smoothed_chroms.size() <= prec_idx)
        {
          throw Exception::IllegalArgument(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION,
            "Tried to calculate peak area and height without any smoothed chromatograms for precursors");
        }
        else if (peak_integration_ == "smoothed")
        {
          used_chromatogram = resampleChromatogram_(smoothed_chroms[prec_idx], master_peak_container, local_left, local_right);
        }
        else
        {
          throw Exception::IllegalArgument(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION,
            String("Peak integration chromatogram ") + peak_integration_ + " is not a valid method for MRMTransitionGroupPicker");
        }
 
        Feature f;
        double quality = 0;
        f.setQuality(0, quality);
        f.setOverallQuality(quality);
 
        PeakIntegrator::PeakArea pa = pi_.integratePeak(used_chromatogram, local_left, local_right);
        double peak_integral = pa.area;
        double peak_apex_int = pa.height;
 
        if (background_subtraction_ != "none")
        {
          double background{0};
          double avg_noise_level{0};
          if ((peak_integration_ == "smoothed") && smoothed_chroms.size() <= prec_idx)
          {
            throw Exception::IllegalArgument(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION,
              "Tried to calculate background estimation without any smoothed chromatograms");
          }
          else if (background_subtraction_ == "original")
          {
            const double intensity_left = chromatogram.PosBegin(local_left)->getIntensity();
            const double intensity_right = (chromatogram.PosEnd(local_right) - 1)->getIntensity();
            const UInt n_points = std::distance(chromatogram.PosBegin(local_left), chromatogram.PosEnd(local_right));
            avg_noise_level = (intensity_right + intensity_left) / 2;
            background = avg_noise_level * n_points;
          }
          else if (background_subtraction_ == "exact")
          {
            PeakIntegrator::PeakBackground pb = pi_.estimateBackground(used_chromatogram, local_left, local_right, pa.apex_pos);
            background = pb.area;
            avg_noise_level = pb.height;
          }
          peak_integral -= background;
          peak_apex_int -= avg_noise_level;
          if (peak_integral < 0) {peak_integral = 0;}
          if (peak_apex_int < 0) {peak_apex_int = 0;}
 
          f.setMetaValue("area_background_level", background);
          f.setMetaValue("noise_background_level", avg_noise_level);
        }
 
        f.setMZ(chromatogram.getPrecursor().getMZ());
        if (k == 0) {mrmFeature.setMZ(chromatogram.getPrecursor().getMZ());} // only use m/z if first (monoisotopic) isotope
 
        if (chromatogram.metaValueExists("precursor_mz")) // legacy code (ensures that old tests still work)
        {
          f.setMZ(chromatogram.getMetaValue("precursor_mz"));
          if (k == 0) {mrmFeature.setMZ(chromatogram.getMetaValue("precursor_mz"));} // only use m/z if first (monoisotopic) isotope
        }
 
        f.setRT(picked_chroms[chr_idx][peak_idx].getMZ());
        f.setIntensity(peak_integral);
        ConvexHull2D hull;
        hull.setHullPoints(pa.hull_points);
        f.getConvexHulls().push_back(hull);
        f.setMetaValue("native_id", chromatogram.getNativeID());
        f.setMetaValue("peak_apex_int", peak_apex_int);
 
        if (use_precursors_ && transition_group.getTransitions().empty())
        {
          total_intensity += peak_integral;
        }
 
        mrmFeature.addPrecursorFeature(f, chromatogram.getNativeID());
      }
    }
 
    // maybe private, but we have tests
 
    template <typename SpectrumT>
    void remove_overlapping_features(std::vector<SpectrumT>& picked_chroms, double best_left, double best_right)
    {
      // delete all seeds that lie within the current seed
      for (Size k = 0; k < picked_chroms.size(); k++)
      {
        for (Size i = 0; i < picked_chroms[k].size(); i++)
        {
          if (picked_chroms[k][i].getMZ() >= best_left && picked_chroms[k][i].getMZ() <= best_right)
          {
            picked_chroms[k][i].setIntensity(0.0);
          }
        }
      }
 
      // delete all seeds that overlap within the current seed
      for (Size k = 0; k < picked_chroms.size(); k++)
      {
        for (Size i = 0; i < picked_chroms[k].size(); i++)
        {
          if (picked_chroms[k][i].getIntensity() <= 0.0) {continue; }
 
          double left = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_LEFTBORDER][i];
          double right = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_RIGHTBORDER][i];
          if ((left > best_left && left < best_right)
             || (right > best_left && right < best_right))
          {
            picked_chroms[k][i].setIntensity(0.0);
          }
        }
      }
    }
 
    void findLargestPeak(const std::vector<MSChromatogram >& picked_chroms, int& chr_idx, int& peak_idx);
 
    void findWidestPeakIndices(const std::vector<MSChromatogram>& picked_chroms, Int& chrom_idx, Int& point_idx) const;
 
protected:
 
    void updateMembers_() override;
 
    MRMTransitionGroupPicker& operator=(const MRMTransitionGroupPicker& rhs);
 
    template <typename SpectrumT, typename TransitionT>
    const SpectrumT& selectChromHelper_(const MRMTransitionGroup<SpectrumT, TransitionT>& transition_group, const String& native_id)
    {
      if (transition_group.hasChromatogram(native_id))
      {
        return transition_group.getChromatogram(native_id);
      }
      else if (transition_group.hasPrecursorChromatogram(native_id))
      {
        return transition_group.getPrecursorChromatogram(native_id);
      }
      else
      {
        throw Exception::IllegalArgument(__FILE__, __LINE__, OPENMS_PRETTY_FUNCTION, "Did not find chromatogram for id '" + native_id + "'.");
      }
    }
 
    template <typename SpectrumT, typename TransitionT>
    double computeQuality_(const MRMTransitionGroup<SpectrumT, TransitionT>& transition_group,
                           const std::vector<SpectrumT>& picked_chroms,
                           const int chr_idx,
                           const double best_left,
                           const double best_right,
                           String& outlier)
    {
      // Resample all chromatograms around the current estimated peak and
      // collect the raw intensities. For resampling, use a bit more on either
      // side to correctly identify shoulders etc.
      double resample_boundary = resample_boundary_; // sample 15 seconds more on each side
      SpectrumT master_peak_container;
      const SpectrumT& ref_chromatogram = selectChromHelper_(transition_group, picked_chroms[chr_idx].getNativeID());
      prepareMasterContainer_(ref_chromatogram, master_peak_container, best_left - resample_boundary, best_right + resample_boundary);
      std::vector<std::vector<double> > all_ints;
      for (Size k = 0; k < picked_chroms.size(); k++)
      {
        const SpectrumT& chromatogram = selectChromHelper_(transition_group, picked_chroms[k].getNativeID());
        const SpectrumT used_chromatogram = resampleChromatogram_(chromatogram, 
            master_peak_container, best_left - resample_boundary, best_right + resample_boundary);
 
        std::vector<double> int_here;
        for (const auto& peak : used_chromatogram) int_here.push_back(peak.getIntensity());
        // Remove chromatograms without a single peak
        double tic = std::accumulate(int_here.begin(), int_here.end(), 0.0);
        if (tic > 0.0) all_ints.push_back(int_here);
      }
 
      // Compute the cross-correlation for the collected intensities
      std::vector<double> mean_shapes;
      std::vector<double> mean_coel;
      for (Size k = 0; k < all_ints.size(); k++)
      {
        std::vector<double> shapes;
        std::vector<double> coel;
        for (Size i = 0; i < all_ints.size(); i++)
        {
          if (i == k) {continue;}
          OpenSwath::Scoring::XCorrArrayType res = OpenSwath::Scoring::normalizedCrossCorrelation(
              all_ints[k], all_ints[i], boost::numeric_cast<int>(all_ints[i].size()), 1);
 
          // the first value is the x-axis (retention time) and should be an int -> it show the lag between the two
          double res_coelution = std::abs(OpenSwath::Scoring::xcorrArrayGetMaxPeak(res)->first);
          double res_shape = std::abs(OpenSwath::Scoring::xcorrArrayGetMaxPeak(res)->second);
 
          shapes.push_back(res_shape);
          coel.push_back(res_coelution);
        }
 
        // We have computed the cross-correlation of chromatogram k against
        // all others. Use the mean of these computations as the value for k.
        OpenSwath::mean_and_stddev msc;
        msc = std::for_each(shapes.begin(), shapes.end(), msc);
        double shapes_mean = msc.mean();
        msc = std::for_each(coel.begin(), coel.end(), msc);
        double coel_mean = msc.mean();
 
        // mean shape scores below 0.5-0.6 should be a real sign of trouble ... !
        // mean coel scores above 3.5 should be a real sign of trouble ... !
        mean_shapes.push_back(shapes_mean);
        mean_coel.push_back(coel_mean);
      }
 
      // find the chromatogram with the minimal shape score and the maximal
      // coelution score -> if it is the same chromatogram, the chance is
      // pretty good that it is different from the others...
      int min_index_shape = std::distance(mean_shapes.begin(), std::min_element(mean_shapes.begin(), mean_shapes.end()));
      int max_index_coel = std::distance(mean_coel.begin(), std::max_element(mean_coel.begin(), mean_coel.end()));
 
      // Look at the picked peaks that are within the current left/right borders
      int missing_peaks = 0;
      int multiple_peaks = 0;
 
      // collect all seeds that lie within the current seed
      std::vector<double> left_borders;
      std::vector<double> right_borders;
      for (Size k = 0; k < picked_chroms.size(); k++)
      {
        double l_tmp;
        double r_tmp;
        double max_int = -1;
 
        int pfound = 0;
        l_tmp = -1;
        r_tmp = -1;
        for (Size i = 0; i < picked_chroms[k].size(); i++)
        {
          if (picked_chroms[k][i].getMZ() >= best_left && picked_chroms[k][i].getMZ() <= best_right)
          {
            pfound++;
            if (picked_chroms[k][i].getIntensity() > max_int)
            {
              max_int = picked_chroms[k][i].getIntensity() > max_int;
              l_tmp = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_LEFTBORDER][i];
              r_tmp = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_RIGHTBORDER][i];
            }
          }
        }
 
        if (l_tmp > 0.0) left_borders.push_back(l_tmp);
        if (r_tmp > 0.0) right_borders.push_back(r_tmp);
 
        if (pfound == 0) missing_peaks++;
        if (pfound > 1) multiple_peaks++;
      }
 
      // Check how many chromatograms had exactly one peak picked between our
      // current left/right borders -> this would be a sign of consistency.
      OPENMS_LOG_DEBUG << " Overall found missing : " << missing_peaks << " and multiple : " << multiple_peaks << std::endl;
 
 
      // Is there one transitions that is very different from the rest (e.g.
      // the same element has a bad shape and a bad coelution score) -> potential outlier
      if (min_index_shape == max_index_coel)
      {
        OPENMS_LOG_DEBUG << " element " << min_index_shape << " is a candidate for removal ... " << std::endl;
        outlier = String(picked_chroms[min_index_shape].getNativeID());
      }
      else
      {
        outlier = "none";
      }
 
      // For the final score (larger is better), consider these scores:
      // - missing_peaks (the more peaks are missing, the worse)
      // - multiple_peaks
      // - mean of the shapes (1 is very good, 0 is bad)
      // - mean of the co-elution scores (0 is good, 1 is ok, above 1 is pretty bad)
      double shape_score = std::accumulate(mean_shapes.begin(), mean_shapes.end(), 0.0) / mean_shapes.size();
      double coel_score = std::accumulate(mean_coel.begin(), mean_coel.end(), 0.0) / mean_coel.size();
      coel_score = (coel_score - 1.0) / 2.0;
 
      double score = shape_score - coel_score - 1.0 * missing_peaks / picked_chroms.size();
 
      OPENMS_LOG_DEBUG << " computed score  " << score << " (from " <<  shape_score << 
        " - " << coel_score << " - " << 1.0 * missing_peaks / picked_chroms.size() << ")" << std::endl;
 
      return score;
    }
 
    template <typename SpectrumT>
    void recalculatePeakBorders_(const std::vector<SpectrumT>& picked_chroms, double& best_left, double& best_right, double max_z)
    {
      // 1. Collect all seeds that lie within the current seed 
      // - Per chromatogram only the most intense one counts, otherwise very
      // - low intense peaks can contribute disproportionally to the voting
      // - procedure.
      std::vector<double> left_borders;
      std::vector<double> right_borders;
      for (Size k = 0; k < picked_chroms.size(); k++)
      {
        double max_int = -1;
        double left = -1;
        double right = -1;
        for (Size i = 0; i < picked_chroms[k].size(); i++)
        {
          if (picked_chroms[k][i].getMZ() >= best_left && picked_chroms[k][i].getMZ() <= best_right)
          {
            if (picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_ABUNDANCE][i] > max_int)
            {
              max_int = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_ABUNDANCE][i];
              left = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_LEFTBORDER][i];
              right = picked_chroms[k].getFloatDataArrays()[PeakPickerMRM::IDX_RIGHTBORDER][i];
            }
          }
        }
        if (max_int > -1 )
        {
          left_borders.push_back(left);
          right_borders.push_back(right);
          OPENMS_LOG_DEBUG << " * " << k << " left boundary " << left_borders.back()   <<  " with int " << max_int << std::endl;
          OPENMS_LOG_DEBUG << " * " << k << " right boundary " << right_borders.back() <<  " with int " << max_int << std::endl;
        }
      }
 
      // Return for empty peak list
      if (right_borders.empty())
      {
        return;
      }
 
      // FEATURE IDEA: instead of Z-score use modified Z-score for small data sets 
      // http://d-scholarship.pitt.edu/7948/1/Seo.pdf
      // http://www.itl.nist.gov/div898/handbook/eda/section3/eda35h.htm
      // 1. calculate median
      // 2. MAD = calculate difference to median for each value -> take median of that
      // 3. Mi = 0.6745*(xi - median) / MAD
 
      // 2. Calculate mean and standard deviation
      // If the coefficient of variation is too large for one border, we use a
      // "pseudo-median" instead of the border of the most intense peak.
      double mean, stdev;
 
      // Right borders
      mean = std::accumulate(right_borders.begin(), right_borders.end(), 0.0) / (double) right_borders.size();
      stdev = std::sqrt(std::inner_product(right_borders.begin(), right_borders.end(), right_borders.begin(), 0.0)
                               / right_borders.size() - mean * mean);
      std::sort(right_borders.begin(), right_borders.end());
 
      OPENMS_LOG_DEBUG << " - Recalculating right peak boundaries " << mean << " mean / best " 
                << best_right << " std " << stdev << " : "  << std::fabs(best_right - mean) / stdev 
                << " coefficient of variation" << std::endl;
 
      // Compare right borders of best transition with the mean
      if (std::fabs(best_right - mean) / stdev > max_z)
      {
        best_right = right_borders[right_borders.size() / 2]; // pseudo median
        OPENMS_LOG_DEBUG << " - Setting right boundary to  " << best_right << std::endl;
      }
 
      // Left borders
      mean = std::accumulate(left_borders.begin(), left_borders.end(), 0.0) / (double) left_borders.size();
      stdev = std::sqrt(std::inner_product(left_borders.begin(), left_borders.end(), left_borders.begin(), 0.0)
                        / left_borders.size() - mean * mean);
      std::sort(left_borders.begin(), left_borders.end());
 
      OPENMS_LOG_DEBUG << " - Recalculating left peak boundaries " << mean << " mean / best " 
                << best_left << " std " << stdev << " : "  << std::fabs(best_left - mean) / stdev 
                << " coefficient of variation" << std::endl;
 
      // Compare left borders of best transition with the mean
      if (std::fabs(best_left - mean)  / stdev > max_z)
      {
        best_left = left_borders[left_borders.size() / 2]; // pseudo median
        OPENMS_LOG_DEBUG << " - Setting left boundary to  " << best_left << std::endl;
      }
 
    }
 
 
 
    template <typename SpectrumT>
    void prepareMasterContainer_(const SpectrumT& ref_chromatogram,
                                 SpectrumT& master_peak_container, double left_boundary, double right_boundary)
    {
      OPENMS_PRECONDITION(master_peak_container.empty(), "Master peak container must be empty")
 
      // get the start / end point of this chromatogram => then add one more
      // point beyond the two boundaries to make the resampling accurate also
      // at the edge.
      typename SpectrumT::const_iterator begin = ref_chromatogram.begin();
      while (begin != ref_chromatogram.end() && begin->getMZ() < left_boundary) {begin++; }
      if (begin != ref_chromatogram.begin()) {begin--; }
 
      typename SpectrumT::const_iterator end = begin;
      while (end != ref_chromatogram.end() && end->getMZ() < right_boundary) {end++; }
      if (end != ref_chromatogram.end()) {end++; }
 
      // resize the master container and set the m/z values to the ones of the master container
      master_peak_container.resize(distance(begin, end)); // initialize to zero
      typename SpectrumT::iterator it = master_peak_container.begin();
      for (typename SpectrumT::const_iterator chrom_it = begin; chrom_it != end; chrom_it++, it++)
      {
        it->setMZ(chrom_it->getMZ());
      }
    }
 
    template <typename SpectrumT>
    SpectrumT resampleChromatogram_(const SpectrumT& chromatogram,
                                    const SpectrumT& master_peak_container, double left_boundary, double right_boundary)
    {
      // get the start / end point of this chromatogram => then add one more
      // point beyond the two boundaries to make the resampling accurate also
      // at the edge.
      typename SpectrumT::const_iterator begin = chromatogram.begin();
      while (begin != chromatogram.end() && begin->getMZ() < left_boundary) {begin++;}
      if (begin != chromatogram.begin()) {begin--;}
 
      typename SpectrumT::const_iterator end = begin;
      while (end != chromatogram.end() && end->getMZ() < right_boundary) {end++;}
      if (end != chromatogram.end()) {end++;}
 
      SpectrumT resampled_peak_container = master_peak_container; // copy the master container, which contains the RT values
      LinearResamplerAlign lresampler;
      lresampler.raster(begin, end, resampled_peak_container.begin(), resampled_peak_container.end());
 
      return resampled_peak_container;
    }
 
 
    // Members
    String peak_integration_;
    String background_subtraction_;
    bool recalculate_peaks_;
    bool use_precursors_;
    bool use_consensus_;
    bool compute_peak_quality_;
    bool compute_peak_shape_metrics_;
    bool compute_total_mi_;
    double min_qual_;
 
    int stop_after_feature_;
    double stop_after_intensity_ratio_;
    double min_peak_width_;
    double recalculate_peaks_max_z_;
    double resample_boundary_;
 
    String boundary_selection_method_;
 
    PeakPickerMRM picker_;
    PeakIntegrator pi_;
  };
}