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/*=========================================================================
Program: Insight Segmentation & Registration Toolkit
Module: itkSymmetricSigmoidTransferFunction.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 __itkSymmetricSigmoidTransferFunction_txx
#define __itkSymmetricSigmoidTransferFunction_txx
#include "itkSymmetricSigmoidTransferFunction.h"
namespace itk
{
namespace Statistics
{
template<class ScalarType>
SymmetricSigmoidTransferFunction<ScalarType>
::SymmetricSigmoidTransferFunction()
{
m_Range = 15.0;
m_Offset = 0.1;
}
template<class ScalarType>
SymmetricSigmoidTransferFunction<ScalarType>
::~SymmetricSigmoidTransferFunction()
{
}
template<class ScalarType>
ScalarType
SymmetricSigmoidTransferFunction<ScalarType>
::Evaluate(const ScalarType& input) const
{
ScalarType val;
if(input<-m_Range)
{
val=-0.5;
}
else if(input>m_Range)
{
val=0.5;
}
else
{
val= (ScalarType)1.0/(1.0+vcl_exp(-input))-0.5;
}
return val;
}
/** Evaluate derivatives */
template<class ScalarType>
ScalarType
SymmetricSigmoidTransferFunction<ScalarType>
::EvaluateDerivative(const ScalarType& input) const
{
ScalarType f = Evaluate(input);
return (m_Offset+(0.25-f*f));
}
/** Print the object */
template<class ScalarType>
void
SymmetricSigmoidTransferFunction<ScalarType>
::PrintSelf( std::ostream& os, Indent indent ) const
{
os << indent << "SumInputFunction(" << this << ")" << std::endl;
os << indent << "m_Range = " << m_Range << std::endl;
os << indent << "m_Offset = " << m_Offset << std::endl;
Superclass::PrintSelf( os, indent );
}
} // end namespace Statistics
} // end namespace itk
#endif
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