ExpDecayOsc.cpp

Go to the documentation of this file.

// 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 "MantidCurveFitting/Functions/ExpDecayOsc.h"
#include "MantidAPI/FunctionFactory.h"
#include <cmath>
 
namespace Mantid::CurveFitting::Functions {
 
using namespace CurveFitting;
 
using namespace Kernel;
 
using namespace API;
 
DECLARE_FUNCTION(ExpDecayOsc)
 
void ExpDecayOsc::init() {
  declareParameter("A", 0.2, "Amplitude at time 0");
  declareParameter("Lambda", 0.2, "Decay rate");
  declareParameter("Frequency", 0.1, "Frequency of oscillation");
  declareParameter("Phi", 0.0, "Phase of oscillation at 0 (in Radians)");
}
 
void ExpDecayOsc::function1D(double *out, const double *xValues, const size_t nData) const {
  const double gA0 = getParameter("A");
  const double gs = getParameter("Lambda");
  const double gf = getParameter("Frequency");
  const double gphi = getParameter("Phi");
 
  for (size_t i = 0; i < nData; i++) {
    double x = xValues[i];
    out[i] = gA0 * exp(-gs * x) * cos(2 * M_PI * gf * x + gphi);
  }
}
 
void ExpDecayOsc::functionDeriv1D(Jacobian *out, const double *xValues, const size_t nData) {
  const double gA0 = getParameter("A");
  const double gs = getParameter("Lambda");
  const double gf = getParameter("Frequency");
  const double gphi = getParameter("Phi");
 
  for (size_t i = 0; i < nData; i++) {
    double x = xValues[i];
    double e = exp(-gs * x);
    double c = cos(2 * M_PI * gf * x + gphi);
    double s = sin(2 * M_PI * gf * x + gphi);
    out->set(i, 0, e * c);            // derivative w.r.t. A (gA0)
    out->set(i, 1, -gA0 * x * e * c); // derivative w.r.t  Lambda (gs)
    out->set(i, 2,
             -gA0 * e * 2 * M_PI * x * s); // derivate w.r.t. Frequency (gf)
    out->set(i, 3, -gA0 * e * s);          // detivative w.r.t Phi (gphi)
  }
}
 
void ExpDecayOsc::setActiveParameter(size_t i, double value) {
  size_t j = i;
 
  if (parameterName(j) == "Phi") {
    // Put angle in range of (-180 to 180] degrees
    double a = fmod(value, 2 * M_PI);
    if (a <= -M_PI)
      a += 2 * M_PI;
    if (a > M_PI)
      a -= 2 * M_PI;
    setParameter(j, a, false);
  } else
    setParameter(j, value, false);
}
 
} // namespace Mantid::CurveFitting::Functions