VectorHelper.cpp

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// Mantid Repository : https://github.com/mantidproject/mantid
//
// Copyright © 2018 ISIS Rutherford Appleton Laboratory UKRI,
//   NScD Oak Ridge National Laboratory, European Spallation Source,
//   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
// SPDX - License - Identifier: GPL - 3.0 +
#include <cmath>
#include <stdexcept>
 
#include "MantidKernel/Memory.h"
#include "MantidKernel/VectorHelper.h"
#include <algorithm>
#include <boost/algorithm/string.hpp>
#include <numeric>
#include <sstream>
 
using std::size_t;
 
namespace {
// edge checks
struct EdgeCheck { // for polymorphic access to functors
  virtual bool operator()(double, double, double) const = 0;
  virtual ~EdgeCheck() = default;
};
 
// Standard check, for linear, log, and power
struct StandardEdgeCheck : EdgeCheck {
  StandardEdgeCheck(double lastBinCoef) : m_lastBinCoef(lastBinCoef) {}
  bool operator()(double xcurr, double xs, double rightEdge) const override {
    return xcurr + (1. + m_lastBinCoef) * xs <= rightEdge;
  }
 
private:
  double m_lastBinCoef;
};
// Reverse log check, for reverse log only
struct ReverseLogEdgeCheck : EdgeCheck {
  bool operator()(double xcurr, double xs, double leftEdge) const override { return xcurr + 2. * xs >= leftEdge; }
};
 
// bin width functions
struct BinWidth { // for polymorphic access to functors
  virtual double operator()(double, double) const = 0;
  virtual ~BinWidth() = default;
};
 
// Linear bin width is just the alpha parameter
struct LinearBinWidth : BinWidth {
  double operator()([[maybe_unused]] double xcurr, double alpha) const override { return alpha; }
};
// Log bin width is current position times the alpha parameter
struct LogBinWidth : BinWidth {
  double operator()(double xcurr, double alpha) const override { return xcurr * alpha; }
};
 
// REVERSE LOGARITHMIC
// we go through a reverse log bin by starting from its end, and working our way back to the beginning
// this way we can define the bins in a recurring way, and with a more obvious closeness with the usual log.
struct ReverseLogBinWidth : BinWidth {
  ReverseLogBinWidth(double leftEdge, double rightEdge) : m_leftEdge(leftEdge), m_rightEdge(rightEdge) {}
  double operator()(double xcurr, double alpha) const override { return (xcurr - m_rightEdge - m_leftEdge) * alpha; }
 
private:
  double m_leftEdge;
  double m_rightEdge;
};
// Power bin width is the alpha parameter divided by the current index to the power
struct PowerBinWidth : BinWidth {
  PowerBinWidth(std::size_t &currDiv, double power) : m_currDiv(&currDiv), m_power(power) {}
  double operator()([[maybe_unused]] double xcurr, double alpha) const override {
    return alpha * std::pow((*m_currDiv)++, -m_power);
  }
 
private:
  std::size_t *const m_currDiv; // the pointed-to changes, but not the pointer
  double m_power;
};
} // namespace
 
namespace Mantid::Kernel::VectorHelper {
 
void validateRebinParameters(std::vector<double> const &params, bool const isPower) {
  size_t numParams = params.size();
  if (numParams < 3 || numParams % 2 != 1) {
    throw std::runtime_error("validateRebinParameters: Invalid number of rebin parameters (" +
                             std::to_string(numParams) + ")! Must be odd number of parameters, 3 or more.");
  }
  double previousEdge = params[0];
  for (size_t i = 1; i < numParams - 1; i += 2) {
    double const binWidth = params[i];
    double const nextEdge = params[i + 1];
    if (previousEdge >= nextEdge) {
      throw std::runtime_error(
          "validateRebinParameters: Bin boundary values must be given in order of increasing value! " +
          std::to_string(previousEdge) + " >= " + std::to_string(nextEdge));
    } else if (binWidth == 0) {
      throw std::runtime_error("validateRebinParameters: Bin width cannot be zero!  Found in range " +
                               std::to_string(previousEdge) + " to " + std::to_string(nextEdge));
    } else if (binWidth < 0 && previousEdge <= 0) {
      throw std::runtime_error("Bin boundaries must be positive for logarithmic binning. Got " +
                               std::to_string(previousEdge) + " to " + std::to_string(nextEdge));
    } else if (binWidth < 0 && isPower) {
      throw std::runtime_error(
          "validateRebinParameters: Cannot use power binning with negative bin width!  Bin width was " +
          std::to_string(binWidth));
    }
    previousEdge = nextEdge;
  }
}
 
std::size_t estimateNumberOfBins(std::vector<double> const &params, double const power) {
  bool const isPower = power > 0 && power <= 1;
  validateRebinParameters(params, isPower);
  double numBins = 1.; // always start with 1 left edge / fencepost
  double previousEdge = params[0];
  for (size_t i = 1; i < params.size() - 1; i += 2) {
    double const binWidth = params[i];
    double const nextEdge = params[i + 1];
    if (binWidth < 0) {
      // LOGARITHMIC BINNING
      // NOTE log or reverse log should have approximately the same number of bins here
      numBins += std::ceil(std::log(nextEdge / previousEdge) / std::log(1. - binWidth));
    } else if (isPower) {
      // POWER BINNING
      // formulas taken from Rebin::validateInputs
      if (power == 1) {
        double constexpr eulerMascheroni = 0.5772156649; // Euler-Mascheroni constant
        numBins += std::exp((nextEdge - previousEdge) / binWidth - eulerMascheroni);
      } else {
        numBins += std::pow(((nextEdge - previousEdge) / binWidth) * (1 - power) + 1, 1 / (1 - power));
      }
    } else if (binWidth > 0) {
      // LINEAR BINNING
      numBins += std::ceil((nextEdge - previousEdge) / binWidth);
    }
    previousEdge = nextEdge;
  }
  if (numBins >= static_cast<double>(std::numeric_limits<std::size_t>::max())) {
    throw std::runtime_error(
        "estimateNumberOfBins: The number of bins requested exceeds the maximum storable by size_t.");
  }
  return static_cast<size_t>(numBins);
}
 
std::size_t createAxisFromRebinParams(const std::vector<double> &params, std::vector<double> &xnew,
                                      const bool resize_xnew, const bool full_bins_only, const double xMinHint,
                                      const double xMaxHint, const bool useReverseLogarithmic, const double power) {
 
  // correctly expand the parameters
  std::vector<double> tmp;
  if (params.size() == 1) {
    if (std::isnan(xMinHint) || std::isnan(xMaxHint)) {
      throw std::runtime_error(
          "createAxisFromRebinParams: xMinHint and xMaxHint must be supplied if params contains only the bin width.");
    }
    tmp = {xMinHint, params.front(), xMaxHint};
  }
  std::vector<double> const &fullParams = params.size() == 1 ? tmp : params;
 
  // This coefficient represents the maximum difference between the size of the last bin and all
  // the other bins.
  // For full_bin_only, we want it so that last bin couldn't be smaller than the previous bin
  double const lastBinCoef = full_bins_only ? 1.0 : 0.25;
  // whether to use power binning
  bool isPower = power > 0 && power <= 1;
 
  // if resize_xnew is true, prepare the vector
  double xcurr = fullParams[0];
  xnew.clear();
  if (resize_xnew) {
    // call to estimateNumberOfBins will also validate the parameters
    size_t neededSize = estimateNumberOfBins(fullParams, power);
    /* detect potential memory overflows
     *  TODO find a way to check against actual available system memory
     *  NOTE use of MemoryStats.availMem() was considered, but introduces large overhead into this hot path
     */
    if (neededSize >= xnew.max_size()) {
      throw std::runtime_error(
          "createAxisFromRebinParams: The number of bins requested exceeds the maximum storable by the output vector.");
    }
    xnew.reserve(neededSize);
    xnew.push_back(xcurr);
  } else {
    // validate the parameters, but don't calculate needed size
    validateRebinParameters(fullParams, isPower);
  }
 
  std::size_t currDiv = 1;
 
  // for each range specified, fill in the axis with correct bin edges
  std::size_t inew = 1; // we start with 1, the leftmost edge
  double leftEdge = fullParams[0];
  for (std::size_t i = 1; i <= fullParams.size() - 1; i += 2) {
    double binParam = fullParams[i];
    double rightEdge = fullParams[i + 1];
    double alpha = std::fabs(binParam);
 
    // functions for calculating bin width and checking if within range
    std::unique_ptr<BinWidth> binWidth(nullptr);
    std::unique_ptr<EdgeCheck> edgeCheck(nullptr);
    if (binParam < 0.0 && useReverseLogarithmic) {
      // REVERSE LOGARITHMIC
      binWidth = std::make_unique<ReverseLogBinWidth>(leftEdge, rightEdge);
      edgeCheck = std::make_unique<ReverseLogEdgeCheck>();
      // for reverse log, we start at the right edge and work back to left; to use the same loop, swap the edges
      // the final edge will be added after the loop, fullParams[i+1]
      xcurr = rightEdge;
      std::swap(leftEdge, rightEdge);
    } else if (binParam < 0.0) {
      // LOGARITHMIC
      binWidth = std::make_unique<LogBinWidth>();
      edgeCheck = std::make_unique<StandardEdgeCheck>(lastBinCoef);
    } else if (isPower) {
      // POWER
      binWidth = std::make_unique<PowerBinWidth>(currDiv, power);
      edgeCheck = std::make_unique<StandardEdgeCheck>(lastBinCoef);
    } else {
      // LINEAR
      binWidth = std::make_unique<LinearBinWidth>();
      edgeCheck = std::make_unique<StandardEdgeCheck>(lastBinCoef);
    }
 
    double xs = (*binWidth)(xcurr, alpha);
    while ((*edgeCheck)(xcurr, xs, rightEdge) || !std::isfinite(xs)) { // let errors fall through
      if (xs == 0.0) {
        // Someone gave a 0-sized step! What a dope.
        throw std::runtime_error("Invalid binning step provided! Can't create binning axis.");
      } else if (!std::isfinite(xs)) {
        throw std::runtime_error("An infinite or NaN value was found in the binning parameters.");
      }
      xcurr = xcurr + xs;
      if (resize_xnew) {
        xnew.push_back(xcurr);
      }
      inew++;
      // prepare for next step
      xs = (*binWidth)(xcurr, alpha);
    }
 
    // handle last edge specially, depending on if full_bins_only is set
    if (!useReverseLogarithmic && full_bins_only) {
      // For full_bins_only, we want to add one more full bin, so that last bin is not bigger than the previous one
      xcurr = xcurr + xs;
    } else {
      // For non full_bins_only, finish by adding as much as is left from the range
      // NOTE for reverse log, the left edge was already added, so we can instead jump to the right edge of this range
      xcurr = fullParams[i + 1];
    }
    if (resize_xnew) {
      xnew.push_back(xcurr);
    }
    inew++;
    // prepare for next range
    leftEdge = xcurr;
  }
  // if using reverse log, some bins were added in wrong order; so sort them
  if (useReverseLogarithmic) {
    std::sort(xnew.begin(), xnew.end());
  }
  return inew;
}
 
void rebin(const std::vector<double> &xold, const std::vector<double> &yold, const std::vector<double> &eold,
           const std::vector<double> &xnew, std::vector<double> &ynew, std::vector<double> &enew, bool distribution,
           bool addition) {
  // Make sure y and e vectors are of correct sizes
  const size_t size_xold = xold.size();
  if (size_xold != (yold.size() + 1) || size_xold != (eold.size() + 1))
    throw std::runtime_error("rebin: old y and error vectors should be of same "
                             "size & 1 shorter than x");
  const size_t size_xnew = xnew.size();
  if (size_xnew != (ynew.size() + 1) || size_xnew != (enew.size() + 1))
    throw std::runtime_error("rebin: new y and error vectors should be of same "
                             "size & 1 shorter than x");
 
  size_t size_yold = yold.size();
  size_t size_ynew = ynew.size();
 
  if (!addition) {
    // Make sure ynew & enew contain zeroes
    std::fill(ynew.begin(), ynew.end(), 0.0);
    std::fill(enew.begin(), enew.end(), 0.0);
  }
 
  size_t iold = 0, inew = 0;
  double width;
 
  while ((inew < size_ynew) && (iold < size_yold)) {
    double xo_low = xold[iold];
    double xo_high = xold[iold + 1];
    double xn_low = xnew[inew];
    double xn_high = xnew[inew + 1];
    if (xn_high <= xo_low)
      inew++; /* old and new bins do not overlap */
    else if (xo_high <= xn_low)
      iold++; /* old and new bins do not overlap */
    else {
      //        delta is the overlap of the bins on the x axis
      // delta = std::min(xo_high, xn_high) - std::max(xo_low, xn_low);
      double delta = xo_high < xn_high ? xo_high : xn_high;
      delta -= xo_low > xn_low ? xo_low : xn_low;
      width = xo_high - xo_low;
      if ((delta <= 0.0) || (width <= 0.0)) {
        // No need to throw here, just return (ynew & enew will be empty)
        // throw std::runtime_error("rebin: no bin overlap detected");
        return;
      }
      /*
       *        yoldp contains counts/unit time, ynew contains counts
       *               enew contains counts**2
       *        ynew has been filled with zeros on creation
       */
      if (distribution) {
        // yold/eold data is distribution
        ynew[inew] += yold[iold] * delta;
        // this error is calculated in the same way as opengenie
        enew[inew] += eold[iold] * eold[iold] * delta * width;
      } else {
        // yold/eold data is not distribution
        // do implicit division of yold by width in summing.... avoiding the
        // need for temporary yold array
        // this method is ~7% faster and uses less memory
        ynew[inew] += yold[iold] * delta / width; // yold=yold/width
        // eold=eold/width, so divide by width**2 compared with distribution
        // calculation
        enew[inew] += eold[iold] * eold[iold] * delta / width;
      }
      if (xn_high > xo_high) {
        iold++;
      } else {
        inew++;
      }
    }
  }
 
  if (!addition) // If using the addition facility, have to do bin width and
                 // sqrt errors externally
  {
    if (distribution) {
      /*
       * convert back to counts/unit time
       */
      for (size_t i = 0; i < size_ynew; ++i) {
        {
          width = xnew[i + 1] - xnew[i];
          if (width != 0.0) {
            ynew[i] /= width;
            enew[i] = sqrt(enew[i]) / width;
          } else {
            throw std::invalid_argument("rebin: Invalid output X array, contains consecutive X values");
          }
        }
      }
    } else {
      // non-distribution, just square root final error value
      using pf = double (*)(double);
      pf uf = std::sqrt;
      std::transform(enew.begin(), enew.end(), enew.begin(), uf);
    }
  }
}
 
//-------------------------------------------------------------------------------------------------
void rebinHistogram(const std::vector<double> &xold, const std::vector<double> &yold, const std::vector<double> &eold,
                    const std::vector<double> &xnew, std::vector<double> &ynew, std::vector<double> &enew,
                    bool addition) {
  // Make sure y and e vectors are of correct sizes
  const size_t size_yold = yold.size();
  if (xold.size() != (size_yold + 1) || size_yold != eold.size())
    throw std::runtime_error("rebin: y and error vectors should be of same size & 1 shorter than x");
  const size_t size_ynew = ynew.size();
  if (xnew.size() != (size_ynew + 1) || size_ynew != enew.size())
    throw std::runtime_error("rebin: y and error vectors should be of same size & 1 shorter than x");
 
  // If not adding to existing vectors, make sure ynew & enew contain zeroes
  if (!addition) {
    ynew.assign(size_ynew, 0.0);
    enew.assign(size_ynew, 0.0);
  }
 
  // Find the starting points to avoid wasting time processing irrelevant bins
  size_t iold = 0, inew = 0; // iold/inew is the bin number under consideration
                             // (counting from 1, so index+1)
  if (xnew.front() > xold.front()) {
    auto it = std::upper_bound(xold.cbegin(), xold.cend(), xnew.front());
    if (it == xold.end())
      return;
    //      throw std::runtime_error("No overlap: max of X-old < min of X-new");
    iold = std::distance(xold.begin(), it) - 1; // Old bin to start at (counting from 0)
  } else {
    auto it = std::upper_bound(xnew.cbegin(), xnew.cend(), xold.front());
    if (it == xnew.cend())
      return;
    //      throw std::runtime_error("No overlap: max of X-new < min of X-old");
    inew = std::distance(xnew.cbegin(), it) - 1; // New bin to start at (counting from 0)
  }
 
  double frac, fracE;
  double oneOverWidth, overlap;
  double temp;
 
  // loop over old vector from starting point calculated above
  for (; iold < size_yold; ++iold) {
    double xold_of_iold_p_1 = xold[iold + 1]; // cache for speed
    // If current old bin is fully enclosed by new bin, just unload the counts
    if (xold_of_iold_p_1 <= xnew[inew + 1]) {
      ynew[inew] += yold[iold];
      temp = eold[iold];
      enew[inew] += temp * temp;
      // If the upper bin boundaries were equal, then increment inew
      if (xold_of_iold_p_1 == xnew[inew + 1])
        inew++;
    } else {
      double xold_of_iold = xold[iold]; // cache for speed
      // This is the counts per unit X in current old bin
      oneOverWidth = 1. / (xold_of_iold_p_1 - xold_of_iold); // cache 1/width to speed things up
      frac = yold[iold] * oneOverWidth;
      temp = eold[iold];
      fracE = temp * temp * oneOverWidth;
 
      // Now loop over bins in new vector overlapping with current 'old' bin
      while (inew < size_ynew && xnew[inew + 1] <= xold_of_iold_p_1) {
        overlap = xnew[inew + 1] - std::max(xnew[inew], xold_of_iold);
        ynew[inew] += frac * overlap;
        enew[inew] += fracE * overlap;
        ++inew;
      }
 
      // Stop if at end of new X range
      if (inew == size_ynew)
        break;
 
      // Unload the rest of the current old bin into the current new bin
      overlap = xold_of_iold_p_1 - xnew[inew];
      ynew[inew] += frac * overlap;
      enew[inew] += fracE * overlap;
    }
  } // loop over old bins
 
  if (!addition) // If this used to add at the same time then not necessary
                 // (should be done externally)
  {
    // Now take the root-square of the errors
    using pf = double (*)(double);
    pf uf = std::sqrt;
    std::transform(enew.begin(), enew.end(), enew.begin(), uf);
  }
}
 
//-------------------------------------------------------------------------------------------------
void convertToBinCentre(const std::vector<double> &bin_edges, std::vector<double> &bin_centres) {
  const std::vector<double>::size_type npoints = bin_edges.size();
  if (bin_centres.size() != npoints) {
    bin_centres.resize(npoints);
  }
 
  // The custom binary function modifies the behaviour of the algorithm to
  // compute the average of
  // two adjacent bin boundaries
  std::adjacent_difference(bin_edges.begin(), bin_edges.end(), bin_centres.begin(), SimpleAverage<double>());
  // The algorithm copies the first element of the input to the first element of
  // the output so we need to
  // remove the first element of the output
  bin_centres.erase(bin_centres.begin());
}
 
//-------------------------------------------------------------------------------------------------
void convertToBinBoundary(const std::vector<double> &bin_centers, std::vector<double> &bin_edges) {
  const auto n = bin_centers.size();
 
  // Special case empty input: output is also empty
  if (n == 0) {
    bin_edges.resize(0);
    return;
  }
 
  bin_edges.resize(n + 1);
 
  // Special case input of size one: we have no means of guessing the bin size,
  // set it to 1.
  if (n == 1) {
    bin_edges[0] = bin_centers[0] - 0.5;
    bin_edges[1] = bin_centers[0] + 0.5;
    return;
  }
 
  for (size_t i = 0; i < n - 1; ++i) {
    bin_edges[i + 1] = 0.5 * (bin_centers[i] + bin_centers[i + 1]);
  }
 
  bin_edges[0] = bin_centers[0] - (bin_edges[1] - bin_centers[0]);
 
  bin_edges[n] = bin_centers[n - 1] + (bin_centers[n - 1] - bin_edges[n - 1]);
}
 
size_t indexOfValueFromCenters(const std::vector<double> &bin_centers, const double value) {
  int index = indexOfValueFromCentersNoThrow(bin_centers, value);
  if (index >= 0)
    return static_cast<size_t>(index);
  else
    throw std::out_of_range("indexOfValue - value out of range");
}
 
int indexOfValueFromCentersNoThrow(const std::vector<double> &bin_centers, const double value) {
  if (bin_centers.empty()) {
    throw std::out_of_range("indexOfValue - vector is empty");
  }
  if (bin_centers.size() == 1) {
    // no mean to guess bin size, assuming 1
    if (value < bin_centers[0] - 0.5 || value > bin_centers[0] + 0.5) {
      return -1;
    } else {
      return 0;
    }
  } else {
    const size_t n = bin_centers.size();
    const double firstBinLowEdge = bin_centers[0] - 0.5 * (bin_centers[1] - bin_centers[0]);
    const double lastBinHighEdge = bin_centers[n - 1] + 0.5 * (bin_centers[n - 1] - bin_centers[n - 2]);
    if (value < firstBinLowEdge || value > lastBinHighEdge) {
      return -1;
    } else {
      const auto it = std::lower_bound(bin_centers.begin(), bin_centers.end(), value);
      if (it == bin_centers.end()) {
        return static_cast<int>(n - 1);
      }
      size_t binIndex = std::distance(bin_centers.begin(), it);
      if (binIndex > 0 &&
          value < bin_centers[binIndex - 1] + 0.5 * (bin_centers[binIndex] - bin_centers[binIndex - 1])) {
        binIndex--;
      }
      return static_cast<int>(binIndex);
    }
  }
}
 
size_t indexOfValueFromEdges(const std::vector<double> &bin_edges, const double value) {
  if (bin_edges.empty()) {
    throw std::out_of_range("indexOfValue - vector is empty");
  }
  if (bin_edges.size() == 1) {
    throw std::out_of_range("indexOfValue - requires at least two bin edges");
  }
  if (value < bin_edges.front()) {
    throw std::out_of_range("indexOfValue - value out of range");
  }
  const auto it = std::lower_bound(bin_edges.begin(), bin_edges.end(), value);
  if (it == bin_edges.end()) {
    throw std::out_of_range("indexOfValue - value out of range");
  }
  // index of closest edge above value is distance of iterator from start
  size_t edgeIndex = std::distance(bin_edges.begin(), it);
  // if the element n is the first that is >= value, then the value is in (n-1)
  // th bin
  if (edgeIndex > 0)
    edgeIndex--;
  return edgeIndex;
}
 
//-------------------------------------------------------------------------------------------------
bool isConstantValue(const std::vector<double> &arra) {
  // make comparisons with the first value
  auto i = arra.cbegin();
 
  if (i == arra.cend()) { // empty array
    return true;
  }
 
  double val(*i);
  // this loop can be entered! NAN values make comparisons difficult because nan
  // != nan, deal with these first
  for (; val != val;) {
    ++i;
    if (i == arra.cend()) {
      // all values are contant (NAN)
      return true;
    }
    val = *i;
  }
 
  for (; i != arra.cend(); ++i) {
    if (*i != val) {
      return false;
    }
  }
  // no different value was found and so every must be equal to c
  return true;
}
 
//-------------------------------------------------------------------------------------------------
template <typename NumT>
std::vector<NumT> splitStringIntoVector(std::string listString, const std::string &separators) {
  // Split the string and turn it into a vector.
  std::vector<NumT> values;
  std::vector<std::string> strs;
 
  boost::split(strs, listString, boost::is_any_of(separators));
  for (auto &str : strs) {
    if (!str.empty()) {
      // String not empty
      std::stringstream oneNumber(str);
      NumT num;
      oneNumber >> num;
      values.emplace_back(num);
    }
  }
  return values;
}
 
//-------------------------------------------------------------------------------------------------
int getBinIndex(const std::vector<double> &bins, const double value) {
  assert(bins.size() >= 2);
  // Since we cast to an int below:
  assert(bins.size() < static_cast<size_t>(std::numeric_limits<int>::max()));
  // If X is below the min value
  if (value < bins.front())
    return 0;
 
  // upper_bound will find the right-hand bin boundary (even if the value is
  // equal to
  // the left-hand one) - hence we subtract 1 from the found point.
  // Since we want to return the LH boundary of the last bin if the value is
  // outside
  // the upper range, we leave the last value out (i.e. bins.end()-1)
  auto it = std::upper_bound(bins.begin(), bins.end() - 1, value) - 1;
  assert(it >= bins.begin());
  // Convert an iterator to an index for the return value
  return static_cast<int>(it - bins.begin());
}
 
//-------------------------------------------------------------------------------------------------
 
namespace {
double runAverage(size_t index, size_t startIndex, size_t endIndex, const double halfWidth,
                  const std::vector<double> &input, std::vector<double> const *const binBndrs) {
 
  size_t iStart, iEnd;
  double weight0(0), weight1(0), start(0.0), end(0.0);
  //
  if (binBndrs) {
    // identify initial and final bins to
    // integrate over. Notice the difference
    // between start and end bin and shift of
    // the interpolating function into the center
    // of each bin
    auto &rBndrs = *binBndrs;
    // bin0 = binBndrs->operator[](index + 1) - binBndrs->operator[](index);
 
    double binC = 0.5 * (rBndrs[index + 1] + rBndrs[index]);
    start = binC - halfWidth;
    end = binC + halfWidth;
    if (start <= rBndrs[startIndex]) {
      iStart = startIndex;
      start = rBndrs[iStart];
    } else {
      iStart = getBinIndex(*binBndrs, start);
      weight0 = (rBndrs[iStart + 1] - start) / (rBndrs[iStart + 1] - rBndrs[iStart]);
      iStart++;
    }
    if (end >= rBndrs[endIndex]) {
      iEnd = endIndex; // the signal defined up to i<iEnd
      end = rBndrs[endIndex];
    } else {
      iEnd = getBinIndex(*binBndrs, end);
      weight1 = (end - rBndrs[iEnd]) / (rBndrs[iEnd + 1] - rBndrs[iEnd]);
    }
    if (iStart > iEnd) { // start and end get into the same bin
      weight1 = 0;
      weight0 = (end - start) / (rBndrs[iStart] - rBndrs[iStart - 1]);
    }
  } else { // integer indexes and functions defined in the bin centers
    auto iHalfWidth = static_cast<size_t>(halfWidth);
    iStart = index - iHalfWidth;
    if (startIndex + iHalfWidth > index)
      iStart = startIndex;
    iEnd = index + iHalfWidth;
    if (iEnd > endIndex)
      iEnd = endIndex;
  }
 
  double avrg = 0;
  size_t ic = 0;
  for (size_t j = iStart; j < iEnd; j++) {
    avrg += input[j];
    ic++;
  }
  if (binBndrs) { // add values at edges
    if (iStart != startIndex)
      avrg += input[iStart - 1] * weight0;
    if (iEnd != endIndex)
      avrg += input[iEnd] * weight1;
 
    double div = end - start;
    if (.0 == div)
      return 0;
    else
      return avrg / (end - start);
  } else {
    if (0 == ic) {
      return 0;
    } else {
      return avrg / double(ic);
    }
  }
}
} // namespace
 
void smoothInRange(const std::vector<double> &input, std::vector<double> &output, const double avrgInterval,
                   std::vector<double> const *const binBndrs, size_t startIndex, size_t endIndex,
                   std::vector<double> *const outBins) {
 
  if (endIndex == 0)
    endIndex = input.size();
  if (endIndex > input.size())
    endIndex = input.size();
 
  if (endIndex <= startIndex) {
    output.resize(0);
    return;
  }
 
  size_t max_size = input.size();
  if (binBndrs) {
    if (binBndrs->size() != max_size + 1) {
      throw std::invalid_argument("Array of bin boundaries, "
                                  "if present, have to be one bigger then the input array");
    }
  }
 
  size_t length = endIndex - startIndex;
  output.resize(length);
 
  double halfWidth = avrgInterval / 2;
  if (!binBndrs) {
    if (std::floor(halfWidth) * 2 - avrgInterval > 1.e-6) {
      halfWidth = std::floor(halfWidth) + 1;
    }
  }
 
  if (outBins)
    outBins->resize(length + 1);
 
  //  Run averaging
  double binSize = 1;
  for (size_t i = startIndex; i < endIndex; i++) {
    if (binBndrs) {
      binSize = binBndrs->operator[](i + 1) - binBndrs->operator[](i);
    }
    output[i - startIndex] = runAverage(i, startIndex, endIndex, halfWidth, input, binBndrs) * binSize;
    if (outBins && binBndrs) {
      outBins->operator[](i - startIndex) = binBndrs->operator[](i);
    }
  }
  if (outBins && binBndrs) {
    outBins->operator[](endIndex - startIndex) = binBndrs->operator[](endIndex);
  }
}
 
template DLLExport std::vector<int32_t> splitStringIntoVector<int32_t>(std::string listString,
                                                                       const std::string &separator);
template DLLExport std::vector<int64_t> splitStringIntoVector<int64_t>(std::string listString,
                                                                       const std::string &separator);
template DLLExport std::vector<size_t> splitStringIntoVector<size_t>(std::string listString,
                                                                     const std::string &separator);
template DLLExport std::vector<float> splitStringIntoVector<float>(std::string listString,
                                                                   const std::string &separator);
template DLLExport std::vector<double> splitStringIntoVector<double>(std::string listString,
                                                                     const std::string &separator);
template DLLExport std::vector<std::string> splitStringIntoVector<std::string>(std::string listString,
                                                                               const std::string &separator);
 
} // namespace Mantid::Kernel::VectorHelper