MaxentEntropyNegativeValues.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/MaxentEntropyNegativeValues.h"
#include <cmath>
 
namespace Mantid::Algorithms {
 
std::vector<double> MaxentEntropyNegativeValues::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++) {
    double normVal = values[i] / background;
    result[i] = -std::log(normVal + std::sqrt(normVal * normVal + 1));
  }
  return result;
}
 
std::vector<double> MaxentEntropyNegativeValues::secondDerivative(const std::vector<double> &values,
                                                                  double background) {
 
  std::vector<double> result(values.size());
 
  double bkg2 = background * background;
 
  // Second derivative
  for (size_t i = 0; i < values.size(); i++) {
    result[i] = std::sqrt(values[i] * values[i] + bkg2);
  }
  return result;
}
 
std::vector<double> MaxentEntropyNegativeValues::correctValues(const std::vector<double> &values, double newValue) {
 
  UNUSED_ARG(newValue)
 
  // Nothing to correct
  return values;
}
 
} // namespace Mantid::Algorithms