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/*=========================================================================
*
* Copyright NumFOCUS
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#ifndef itkMixtureModelComponentBase_h
#define itkMixtureModelComponentBase_h
#include "vnl/vnl_vector.h"
#include "vnl/vnl_matrix.h"
#include "itkArray.h"
#include "itkObject.h"
#include "itkMembershipFunctionBase.h"
namespace itk
{
namespace Statistics
{
/**
* \class MixtureModelComponentBase
* \brief base class for distribution modules that supports analytical way
* to update the distribution parameters
*
* This class expects that its subclasses (distribution components) should
* have analytical expressions for updating its parameters using only
* the measurement vectors and their associated weights.
*
* This class can be considered as a macro class that encapsulates the
* storage for the weights, model (subclasses of MembershipFunctionBase),
* and model parameter estimators (implementation of analytical expressions).
*
* Subclasses of this class should define their own distribution specific
* membership function. For example, GaussianMixtureModelComponent class
* defines and creates a GaussianDensityFunction object for that matter.
* Subclasses should also cast such membership function object to
* MembershipFunctionBase object. By doing that, users can get pointers
* to membership functions from different distributional model
*
* \sa ExpectationMaximizationMixtureModelEstimator
* \ingroup ITKStatistics
*/
template <typename TSample>
class ITK_TEMPLATE_EXPORT MixtureModelComponentBase : public Object
{
public:
/**Standard class type aliases. */
using Self = MixtureModelComponentBase;
using Superclass = Object;
using Pointer = SmartPointer<Self>;
using ConstPointer = SmartPointer<const Self>;
/**Standard Macros */
itkOverrideGetNameOfClassMacro(MixtureModelComponentBase);
using MeasurementVectorType = typename TSample::MeasurementVectorType;
using MeasurementVectorSizeType = typename TSample::MeasurementVectorSizeType;
/** type alias for the MembershipFunctionBase */
using MembershipFunctionType = MembershipFunctionBase<MeasurementVectorType>;
/** type alias of storage for the weights */
using WeightArrayType = Array<double>;
using ParametersType = Array<double>;
/** stores the sample pointer */
virtual void
SetSample(const TSample * sample);
/** returns the sample pointer */
const TSample *
GetSample() const;
/** returns the pointer to the membership function object.
* Subclasses of this class are responsible for creating the
* actual membership function objects and cast them to
* MembershipFunctionBase objects */
MembershipFunctionType *
GetMembershipFunction();
void
SetMinimalParametersChange(double change)
{
m_MinimalParametersChange = change;
}
double
GetMinimalParametersChange()
{
return m_MinimalParametersChange;
}
virtual void
SetParameters(const ParametersType & parameters);
virtual ParametersType
GetFullParameters()
{
return m_Parameters;
}
/** sets the parameters modified tag. if one or more of the membership
* function's parameters are changed, then flag should be true */
void
AreParametersModified(bool flag);
/** returns the value of parameter modified tag */
bool
AreParametersModified();
/** sets the index-th weight with the "value" */
void
SetWeight(unsigned int index, double value);
/** returns the index-th weight */
double
GetWeight(unsigned int index) const;
/** returns the membership score of the "measurements" vector */
double
Evaluate(MeasurementVectorType & measurements);
/** returns the pointer to the weights array */
itkGetConstReferenceMacro(Weights, WeightArrayType);
virtual void
Update();
protected:
MixtureModelComponentBase();
~MixtureModelComponentBase() override = default;
void
PrintSelf(std::ostream & os, Indent indent) const override;
/** stores the pointer to the membership function.
* subclasses use this function to store their membership function
* object after dynamic creation */
void
SetMembershipFunction(MembershipFunctionType * function);
virtual void
GenerateData() = 0;
private:
/** target sample data pointer */
const TSample * m_Sample{};
double m_MinimalParametersChange{};
ParametersType m_Parameters{};
/** SmartPointer to the membership function - usually density function */
MembershipFunctionType * m_MembershipFunction{};
/** weights array */
WeightArrayType m_Weights{};
/** indicative flag of membership function's parameter changes */
bool m_ParametersModified{};
}; // end of class
} // end of namespace Statistics
} // end of namespace itk
#ifndef ITK_MANUAL_INSTANTIATION
# include "itkMixtureModelComponentBase.hxx"
#endif
#endif
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