PolynomialCorrection.cpp

// 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 +
//----------------------------------------------------------------------
// Includes
//----------------------------------------------------------------------
#include "MantidAlgorithms/PolynomialCorrection.h"
#include "MantidKernel/ArrayProperty.h"
#include "MantidKernel/ListValidator.h"
#include "MantidKernel/MandatoryValidator.h"
#include <cmath>

using namespace Mantid::API;
using namespace Mantid::Kernel;

namespace Mantid::Algorithms {
// Register the class into the algorithm factory
DECLARE_ALGORITHM(PolynomialCorrection)

PolynomialCorrection::PolynomialCorrection()
    : UnaryOperation(), m_coeffs(), m_polySize(), m_isOperationMultiply(false) {}

void PolynomialCorrection::defineProperties() {
  // We need an array property for the coefficients of the polynomial: C0 + C1*x
  // + C2*x*x + ....
  declareProperty(std::make_unique<ArrayProperty<double>>("Coefficients",
                                                          std::make_shared<MandatoryValidator<std::vector<double>>>()),
                  "Array Property containing the coefficients of the polynomial correction "
                  "function in ascending powers of X. Can be given as a comma separated "
                  "list in string form.");
  std::vector<std::string> propOptions{"Multiply", "Divide"};
  declareProperty("Operation", "Multiply", std::make_shared<StringListValidator>(propOptions),
                  "The operation with which the correction is applied to the "
                  "data (default: Multiply)");
}

void PolynomialCorrection::retrieveProperties() {
  // So this will be m_coeffs[0] + m_coeffs[1]*x + m_coeffs[2]*x^2 + ...
  m_coeffs = getProperty("Coefficients");
  m_polySize = m_coeffs.size();
  std::string operation = getProperty("Operation");
  m_isOperationMultiply = operation == "Multiply";
}

void PolynomialCorrection::performUnaryOperation(const double XIn, const double YIn, const double EIn, double &YOut,
                                                 double &EOut) {
  // The first value of the coefficients vector is for the zeroth power of X.
  double factor = m_coeffs[0];
  double xPow = 1.0;
  // Build up the polynomial in ascending powers of x
  for (std::vector<double>::size_type i = 1; i < m_polySize; ++i) {
    xPow *= XIn;
    factor += m_coeffs[i] * xPow;
  }

  // Apply the  correction factor to the data and error
  if (m_isOperationMultiply) {
    YOut = YIn * factor;
    EOut = EIn * std::abs(factor);
  } else {
    YOut = YIn / factor;
    EOut = EIn / std::abs(factor);
  }
}

} // namespace Mantid::Algorithms