PhaseFitter.h

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// phasefitter.h: Class to perform phase fitting (TEC), allowing phase wraps
// Copyright (C) 2020 ASTRON (Netherlands Institute for Radio Astronomy)
// SPDX-License-Identifier: GPL-3.0-or-later
//
 
#ifndef PHASE_FITTER_H
#define PHASE_FITTER_H
 
#include <vector>
#include <cmath>
#include <cstring>
 
class PhaseFitter {
 public:
  PhaseFitter()
      : _phases(), _frequencies(), _weights(), _fittingAccuracy(1e-6) {}
 
  PhaseFitter(size_t channelCount)
      : _phases(channelCount, 0.0),
        _frequencies(channelCount, 0.0),
        _weights(channelCount, 1.0),
        _fittingAccuracy(1e-6) {}
 
  void Initialize(const std::vector<double>& frequencies) {
    _phases.assign(frequencies.size(), 0.0);
    _frequencies = frequencies;
    _weights.assign(frequencies.size(), 1.0);
  }
 
  double FitDataToTEC2Model(double& alpha, double& beta);
 
  void FitDataToTEC2Model() {
    double a, b;
    FitDataToTEC2Model(a, b);
  }
 
  double FitDataToTEC2ModelWithInitialValues(double& alpha, double& beta) {
    return FitDataToTEC2Model(alpha, beta);
  }
 
  void FitTEC2ModelParameters(double& alpha, double& beta) const;
 
  double* PhaseData() { return _phases.data(); }
 
  const double* PhaseData() const { return _phases.data(); }
 
  const std::vector<double>& GetFrequencies() const { return _frequencies; }
 
  double* WeightData() { return _weights.data(); }
 
  const double* WeightData() const { return _weights.data(); }
 
  size_t Size() const { return _phases.size(); }
 
  double FittingAccuracy() const { return _fittingAccuracy; }
 
  void SetFittingAccuracy(double newAccuracy) {
    _fittingAccuracy = newAccuracy;
  }
 
  double TEC2ModelCost(double alpha, double beta) const;
 
  static double TEC2ModelFunc(double nu, double alpha, double beta) {
    return alpha / nu + beta;
  }
 
  double FitDataToTEC1Model(double& alpha);
 
  void FitDataToTEC1Model() {
    double a;
    FitDataToTEC1Model(a);
  }
 
  static double TEC2ModelFuncWrapped(double nu, double alpha, double beta) {
    return fmod(alpha / nu + beta, 2.0 * M_PI);
  }
 
  double FitDataToTEC1ModelWithInitialValues(double& alpha) {
    return FitDataToTEC1Model(alpha);
  }
 
  void FitTEC1ModelParameters(double& alpha) const;
 
  double TEC1ModelCost(double alpha) const;
 
  static double TEC1ModelFuncWrapped(double nu, double alpha) {
    return fmod(alpha / nu, 2.0 * M_PI);
  }
 
  static double AlphaToTEC(double alpha) { return alpha / -8.44797245e9; }
 
 private:
  std::vector<double> _phases, _frequencies, _weights;
  double _fittingAccuracy;
 
  double fitTEC2ModelBeta(double alpha, double betaEstimate) const;
  void bruteForceSearchTEC2Model(double& lowerAlpha, double& upperAlpha,
                                 double& beta) const;
  double ternarySearchTEC2ModelAlpha(double startAlpha, double endAlpha,
                                     double& beta) const;
  void fillDataWithTEC2Model(double alpha, double beta);
  void fillDataWithTEC1Model(double alpha);
 
  void bruteForceSearchTEC1Model(double& lowerAlpha, double& upperAlpha) const;
  double ternarySearchTEC1ModelAlpha(double startAlpha, double endAlpha) const;
};
 
#endif