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/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: itkSigmoidTransferFunction.txx
Language: C++
Date: $Date$
Version: $Revision$
Copyright (c) Insight Software Consortium. All rights reserved.
See ITKCopyright.txt or http://www.itk.org/HTML/Copyright.htm for details.
This software is distributed WITHOUT ANY WARRANTY; without even
the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the above copyright notices for more information.
=========================================================================*/
#ifndef __itkSigmoidTransferFunction_txx
#define __itkSigmoidTransferFunction_txx
#include "itkSigmoidTransferFunction.h"
namespace itk
{
namespace Statistics
{
/** Constructor */
template<class ScalarType>
SigmoidTransferFunction< ScalarType>
::SigmoidTransferFunction()
{
m_Alpha = 1.0;
m_Beta = 0.0;
m_OutputMinimum = NumericTraits<ScalarType>::min();
m_OutputMaximum = NumericTraits<ScalarType>::max();
}
/** Destructor */
template<class ScalarType>
SigmoidTransferFunction<ScalarType>
::~SigmoidTransferFunction()
{
}
/** Evaluate */
template<class ScalarType>
ScalarType
SigmoidTransferFunction<ScalarType>
::Evaluate(const ScalarType& input) const
{
const ScalarType x = (static_cast<ScalarType>(input) - m_Beta) / m_Alpha;
const ScalarType e = 1.0 / (1.0 + vcl_exp(-x));
const ScalarType v = (m_OutputMaximum - m_OutputMinimum) * e
+ m_OutputMinimum;
return v;
}
/** Evaluate Derivatives */
template<class ScalarType>
ScalarType
SigmoidTransferFunction< ScalarType>
::EvaluateDerivative(const ScalarType& input) const
{
ScalarType f = Evaluate(input);
return f * (1 - f);
}
/** Print the object */
template<class ScalarType>
void
SigmoidTransferFunction<ScalarType>
::PrintSelf( std::ostream& os, Indent indent ) const
{
os << indent << "SigmoidTransferFunction(" << this << ")" << std::endl;
os << indent << "m_Alpha = " << m_Alpha << std::endl;
os << indent << "m_Beta = " << m_Beta << std::endl;
os << indent << "m_OutputMinimum = " << m_OutputMinimum << std::endl;
os << indent << "m_OutputMaximum = " << m_OutputMaximum << std::endl;
Superclass::PrintSelf( os, indent );
}
} // end namespace Statistics
} // end namespace itk
#endif
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