Polynomial.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 "MantidCurveFitting/Functions/Polynomial.h"
#include "MantidAPI/FunctionFactory.h"
 
using namespace Mantid::Kernel;
 
using namespace Mantid::API;
 
using namespace std;
 
namespace Mantid::CurveFitting::Functions {
 
using namespace CurveFitting;
 
DECLARE_FUNCTION(Polynomial)
 
//----------------------------------------------------------------------------------------------
Polynomial::Polynomial() : m_n(0) {
  declareParameter("A0");
  declareAttribute("n", Attribute(0));
}
 
//----------------------------------------------------------------------------------------------
void Polynomial::function1D(double *out, const double *xValues, const size_t nData) const {
  // 1. Use a vector for all coefficient
  vector<double> coeff(m_n + 1, 0.0);
  for (int i = 0; i < m_n + 1; ++i)
    coeff[i] = getParameter(i);
 
  // 2. Calculate
  for (size_t i = 0; i < nData; ++i) {
    double x = xValues[i];
    double temp = coeff[0];
    double nx = x;
    for (int j = 1; j <= m_n; ++j) {
      temp += coeff[j] * nx;
      nx *= x;
    }
    out[i] = temp;
  }
}
 
//----------------------------------------------------------------------------------------------
void Polynomial::functionDeriv1D(API::Jacobian *out, const double *xValues, const size_t nData) {
  for (size_t i = 0; i < nData; i++) {
    double x = xValues[i];
    double nx = 1;
    for (int j = 0; j <= m_n; ++j) {
      out->set(i, j, nx);
      nx *= x;
    }
  }
}
 
//----------------------------------------------------------------------------------------------
std::vector<std::string> Polynomial::getAttributeNames() const { return {"n"}; }
 
//----------------------------------------------------------------------------------------------
API::IFunction::Attribute Polynomial::getAttribute(const std::string &attName) const {
  if (attName == "n") {
    return Attribute(m_n);
  }
 
  throw std::invalid_argument("Polynomial: Unknown attribute " + attName);
}
 
//----------------------------------------------------------------------------------------------
void Polynomial::setAttribute(const std::string &attName, const API::IFunction::Attribute &att) {
  if (attName == "n") {
    // set the polynomial order
 
    auto newN = att.asInt();
    if (newN < 0) {
      throw std::invalid_argument("Polynomial: polynomial order cannot be negative.");
    }
 
    // Save old values
    std::vector<double> oldValues(std::min(m_n, newN) + 1);
    for (size_t i = 0; i < oldValues.size(); ++i) {
      oldValues[i] = getParameter(i);
    }
 
    if (m_n >= 0) {
      clearAllParameters();
    }
    m_n = att.asInt();
    for (int i = 0; i <= m_n; ++i) {
      std::string parName = "A" + std::to_string(i);
      declareParameter(parName);
    }
 
    // Reset old values to new parameters
    for (size_t i = 0; i < oldValues.size(); ++i) {
      setParameter(i, oldValues[i]);
    }
  }
}
 
//----------------------------------------------------------------------------------------------
bool Polynomial::hasAttribute(const std::string &attName) const { return attName == "n"; }
 
} // namespace Mantid::CurveFitting::Functions