BornAgain  1.19.79
Open-source research software to simulate and fit neutron and x-ray reflectometry and grazing-incidence small-angle scattering
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Chi2Metric Class Reference

Description

Implementation of the standard $ \chi^2 $ metric derived from maximum likelihood with Gaussian uncertainties. With default L2 norm corresponds to the formula.

\[\chi^2 = \sum \frac{(I - D)^2}{\delta_D^2}\]

Definition at line 77 of file ObjectiveMetric.h.

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Public Member Functions

 Chi2Metric ()
 
Chi2Metric * clone () const override
 
virtual double compute (const SimDataPair &data_pair, bool use_weights) const
 Computes metric value from SimDataPair object. Calls computeFromArrays internally. More...
 
double computeFromArrays (std::vector< double > sim_data, std::vector< double > exp_data, std::vector< double > exp_stdv, std::vector< double > weight_factors) const override
 Computes metric value from data arrays. Negative values in exp_data are ignored as well as non-positive weight_factors and uncertainties. All arrays involved in the computation must be of the same size. More...
 
double computeFromArrays (std::vector< double > sim_data, std::vector< double > exp_data, std::vector< double > weight_factors) const override
 Computes metric value from data arrays. Negative values in exp_data are ignored as well as non-positive weight_factors. All arrays involved in the computation must be of the same size. More...
 
auto norm () const
 Returns a copy of the normalization function used. More...
 
void setNorm (std::function< double(double)> norm)
 
virtual void transferToCPP ()
 Used for Python overriding of clone (see swig/tweaks.py) More...
 

Private Attributes

std::function< double(double)> m_norm
 

Constructor & Destructor Documentation

◆ Chi2Metric()

Chi2Metric::Chi2Metric ( )

Definition at line 86 of file ObjectiveMetric.cpp.

87  : ObjectiveMetric(ObjectiveMetricUtils::l2Norm())
88 {
89 }
ObjectiveMetric::ObjectiveMetric
ObjectiveMetric(std::function< double(double)> norm)
Definition: ObjectiveMetric.cpp:61
ObjectiveMetricUtils::l2Norm
std::function< double(double)> l2Norm()
Returns L2 normalization function.
Definition: ObjectiveMetricUtils.cpp:56

Member Function Documentation

◆ clone()

Chi2Metric * Chi2Metric::clone ( ) const
overridevirtual

Implements ObjectiveMetric.

Reimplemented in RQ4Metric, meanRelativeDifferenceMetric, and PoissonLikeMetric.

Definition at line 91 of file ObjectiveMetric.cpp.

92 {
93  return copyMetric(*this);
94 }

◆ compute()

double ObjectiveMetric::compute ( const SimDataPair &  data_pair,
bool  use_weights 
) const
virtualinherited

Computes metric value from SimDataPair object. Calls computeFromArrays internally.

Parameters
data_pairSimDataPair object. Can optionally contain data uncertainties
use_weightsboolean, defines if data uncertainties should be taken into account

Reimplemented in RQ4Metric.

Definition at line 66 of file ObjectiveMetric.cpp.

67 {
68  if (use_weights && !data_pair.containsUncertainties())
69  throw std::runtime_error("Error in ObjectiveMetric::compute: the metric is weighted, but "
70  "the simulation-data pair does not contain uncertainties");
71 
72  if (use_weights)
73  return computeFromArrays(data_pair.simulation_array(), data_pair.experimental_array(),
74  data_pair.uncertainties_array(), data_pair.user_weights_array());
75  return computeFromArrays(data_pair.simulation_array(), data_pair.experimental_array(),
76  data_pair.user_weights_array());
77 }
ObjectiveMetric::computeFromArrays
virtual double computeFromArrays(std::vector< double > sim_data, std::vector< double > exp_data, std::vector< double > exp_stdv, std::vector< double > weight_factors) const =0
Computes metric value from data arrays. Negative values in exp_data are ignored as well as non-positi...
SimDataPair::experimental_array
std::vector< double > experimental_array() const
Returns the flattened experimental data cut to the ROI area.
Definition: SimDataPair.cpp:219
SimDataPair::user_weights_array
std::vector< double > user_weights_array() const
Returns a flat array of user weights cut to the ROI area.
Definition: SimDataPair.cpp:240
SimDataPair::uncertainties_array
std::vector< double > uncertainties_array() const
Returns the flattened experimental uncertainties cut to the ROI area. If no uncertainties are availab...
Definition: SimDataPair.cpp:233
SimDataPair::simulation_array
std::vector< double > simulation_array() const
Returns the flattened simulated intensities cut to the ROI area.
Definition: SimDataPair.cpp:226
SimDataPair::containsUncertainties
bool containsUncertainties() const
Definition: SimDataPair.cpp:159

References ObjectiveMetric::computeFromArrays(), SimDataPair::containsUncertainties(), SimDataPair::experimental_array(), SimDataPair::simulation_array(), SimDataPair::uncertainties_array(), and SimDataPair::user_weights_array().

Referenced by RQ4Metric::compute().

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◆ computeFromArrays() [1/2]

double Chi2Metric::computeFromArrays ( std::vector< double >  sim_data,
std::vector< double >  exp_data,
std::vector< double >  exp_stdv,
std::vector< double >  weight_factors 
) const
overridevirtual

Computes metric value from data arrays. Negative values in exp_data are ignored as well as non-positive weight_factors and uncertainties. All arrays involved in the computation must be of the same size.

Parameters
sim_dataarray with simulated intensities.
exp_dataarray with intensity values obtained from an experiment.
exp_stdvarray with experimental data uncertainties.
weight_factorsuser-defined weighting factors. Used linearly, no matter which norm is chosen.

Implements ObjectiveMetric.

Definition at line 96 of file ObjectiveMetric.cpp.

99 {
100  checkIntegrity(sim_data, exp_data, exp_stdv, weight_factors);
101 
102  double result = 0.0;
103  auto norm_fun = norm();
104  for (size_t i = 0, sim_size = sim_data.size(); i < sim_size; ++i)
105  if (exp_data[i] >= 0.0 && weight_factors[i] > 0.0 && exp_stdv[i] > 0.0)
106  result += norm_fun((exp_data[i] - sim_data[i]) / exp_stdv[i]) * weight_factors[i];
107 
108  return std::isfinite(result) ? result : double_max;
109 }
ObjectiveMetric::norm
auto norm() const
Returns a copy of the normalization function used.
Definition: ObjectiveMetric.h:67

Referenced by RQ4Metric::compute().

◆ computeFromArrays() [2/2]

double Chi2Metric::computeFromArrays ( std::vector< double >  sim_data,
std::vector< double >  exp_data,
std::vector< double >  weight_factors 
) const
overridevirtual

Computes metric value from data arrays. Negative values in exp_data are ignored as well as non-positive weight_factors. All arrays involved in the computation must be of the same size.

Parameters
sim_dataarray with simulated intensities.
exp_dataarray with intensity values obtained from an experiment.
weight_factorsuser-defined weighting factors. Used linearly, no matter which norm is chosen.

Implements ObjectiveMetric.

Reimplemented in meanRelativeDifferenceMetric, and PoissonLikeMetric.

Definition at line 111 of file ObjectiveMetric.cpp.

113 {
114  checkIntegrity(sim_data, exp_data, weight_factors);
115 
116  auto norm_fun = norm();
117  double result = 0.0;
118  for (size_t i = 0, sim_size = sim_data.size(); i < sim_size; ++i)
119  if (exp_data[i] >= 0.0 && weight_factors[i] > 0.0)
120  result += norm_fun(exp_data[i] - sim_data[i]) * weight_factors[i];
121 
122  return std::isfinite(result) ? result : double_max;
123 }

References ObjectiveMetric::norm().

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◆ norm()

auto ObjectiveMetric::norm ( ) const
inlineinherited

Returns a copy of the normalization function used.

Definition at line 67 of file ObjectiveMetric.h.

67 { return m_norm; }
ObjectiveMetric::m_norm
std::function< double(double)> m_norm
Definition: ObjectiveMetric.h:70

References ObjectiveMetric::m_norm.

Referenced by LogMetric::computeFromArrays(), computeFromArrays(), PoissonLikeMetric::computeFromArrays(), meanRelativeDifferenceMetric::computeFromArrays(), and ObjectiveMetric::setNorm().

◆ setNorm()

void ObjectiveMetric::setNorm ( std::function< double(double)>  norm)
inherited

Definition at line 79 of file ObjectiveMetric.cpp.

80 {
81  m_norm = std::move(norm);
82 }

References ObjectiveMetric::m_norm, and ObjectiveMetric::norm().

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◆ transferToCPP()

virtual void ICloneable::transferToCPP ( )
inlinevirtualinherited

Used for Python overriding of clone (see swig/tweaks.py)

Definition at line 32 of file ICloneable.h.

Member Data Documentation

◆ m_norm

std::function<double(double)> ObjectiveMetric::m_norm
privateinherited

Definition at line 70 of file ObjectiveMetric.h.

Referenced by ObjectiveMetric::norm(), and ObjectiveMetric::setNorm().

The documentation for this class was generated from the following files: