ProductLinearExp.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/ProductLinearExp.h"
#include "MantidAPI/FunctionFactory.h"
#include "MantidCurveFitting/Functions/ExpDecay.h"
#include "MantidCurveFitting/Functions/LinearBackground.h"
#include "MantidCurveFitting/Functions/ProductFunction.h"
 
namespace Mantid::CurveFitting::Functions {
 
using namespace CurveFitting;
 
using namespace Kernel;
 
using namespace API;
 
DECLARE_FUNCTION(ProductLinearExp)
 
//----------------------------------------------------------------------------------------------
ProductLinearExp::ProductLinearExp() {
  declareParameter("A0", 1.0, "Coefficient for constant term");
  declareParameter("A1", 1.0, "Coefficient for linear term");
  declareParameter("Height", 1.0, "Height");
  declareParameter("Lifetime", 1.0, "Lifetime");
}
 
void ProductLinearExp::functionDeriv1D(API::Jacobian *out, const double *xValues, const size_t nData) {
  const double A0 = getParameter("A0");
  const double A1 = getParameter("A1");
  const double Height = getParameter("Height");
  const double Lifetime = getParameter("Lifetime");
 
  for (size_t i = 0; i < nData; i++) {
    double x = xValues[i];
    double expComponent = Height * std::exp(-x / Lifetime);
    double linearComponent = (A1 * x) + A0;
 
    out->set(i, 0, A1 * x * expComponent);
    out->set(i, 1, (x + A0) * expComponent);
    out->set(i, 2, linearComponent * expComponent / Height);
    out->set(i, 3, linearComponent * expComponent * x / (Lifetime * Lifetime));
  }
}
 
void ProductLinearExp::function1D(double *out, const double *xValues, const size_t nData) const {
  const double A0 = getParameter("A0");
  const double A1 = getParameter("A1");
  const double Height = getParameter("Height");
  const double Lifetime = getParameter("Lifetime");
 
  for (size_t i = 0; i < nData; ++i) {
    out[i] = ((A1 * xValues[i]) + A0) * Height * std::exp(-xValues[i] / Lifetime);
  }
}
 
} // namespace Mantid::CurveFitting::Functions