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/*=========================================================================
*
* Copyright Insight Software Consortium
*
* 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
*
* http://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 itkSigmoidTransferFunction_hxx
#define itkSigmoidTransferFunction_hxx
#include "itkSigmoidTransferFunction.h"
namespace itk
{
namespace Statistics
{
template<typename TScalar>
SigmoidTransferFunction<TScalar>
::SigmoidTransferFunction()
{
m_Alpha = 1.0;
m_Beta = 0.0;
m_OutputMinimum = NumericTraits<ScalarType>::min();
m_OutputMaximum = NumericTraits<ScalarType>::max();
}
template<typename TScalar>
SigmoidTransferFunction<TScalar>
::~SigmoidTransferFunction()
{
}
template<typename TScalar>
TScalar
SigmoidTransferFunction<TScalar>
::Evaluate(const ScalarType& input) const
{
const RealType x = static_cast< RealType >( input - m_Beta ) / m_Alpha;
const RealType e = 1.0 / (1.0 + std::exp( static_cast< typename NumericTraits< ScalarType >::RealType >(-x)));
const ScalarType v = static_cast< ScalarType >( (m_OutputMaximum - m_OutputMinimum) * e )
+ m_OutputMinimum;
return v;
}
template<typename TScalar>
TScalar
SigmoidTransferFunction<TScalar>
::EvaluateDerivative(const ScalarType& input) const
{
ScalarType f = Evaluate(input);
return f * (1 - f);
}
template<typename TScalar>
void
SigmoidTransferFunction<TScalar>
::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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