MaxentEntropyPositiveValues.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 "MantidAlgorithms/MaxEnt/MaxentEntropyPositiveValues.h"
#include <cmath>
 
namespace Mantid::Algorithms {
 
std::vector<double> MaxentEntropyPositiveValues::derivative(const std::vector<double> &values, double background) {
 
  std::vector<double> result(values.size());
 
  // First derivative
  for (size_t i = 0; i < values.size(); i++) {
    result[i] = -std::log(values[i] / background);
  }
  return result;
}
 
std::vector<double> MaxentEntropyPositiveValues::secondDerivative(const std::vector<double> &values,
                                                                  double background) {
 
  UNUSED_ARG(background);
  // This is referred to as 'second derivative' in the paper, but in the codes
  // I've seen is just the input vector
  return values;
}
 
std::vector<double> MaxentEntropyPositiveValues::correctValues(const std::vector<double> &values, double newValue) {
 
  std::vector<double> result(values.size());
 
  for (size_t i = 0; i < values.size(); i++) {
    if (values[i] < 0)
      result[i] = newValue;
    else
      result[i] = values[i];
  }
 
  return result;
}
 
} // namespace Mantid::Algorithms