itkcovariancecalculator.txx

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/*=========================================================================

  Program:   Insight Segmentation & Registration Toolkit
  Module:    $RCSfile: itkCovarianceCalculator.txx,v $
  Language:  C++
  Date:      $Date: 2008-06-27 12:57:43 $
  Version:   $Revision: 1.19 $

  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 __itkCovarianceCalculator_txx
#define __itkCovarianceCalculator_txx

#include "itkCovarianceCalculator.h"

namespace itk{ 
namespace Statistics{

template< class TSample >
CovarianceCalculator< TSample >
::CovarianceCalculator() : 
  m_Mean( 0 ),
  m_InternalMean( 0 )
{
}

template< class TSample >
CovarianceCalculator< TSample >
::~CovarianceCalculator()
{
  if ( m_InternalMean != 0 )
    {
    delete m_InternalMean ;
    m_InternalMean = 0 ;
    }
}

template< class TSample >
void
CovarianceCalculator< TSample >
::PrintSelf(std::ostream& os, Indent indent) const
{
  Superclass::PrintSelf(os,indent);

  os << indent << "Output: " << m_Output << std::endl;

  if ( m_Mean != 0)
    {
    os << indent << "Mean: [" << *m_Mean << "]" << std::endl ;
    }
  else
    {
    os << indent << "Mean: not set" << std::endl ;
    }

  if ( m_InternalMean != 0)
    {
    os << indent << "Internal Mean: [" << *m_InternalMean << "]" << std::endl ;
    }
  else
    {
    os << indent << "Internal Mean: not used" << std::endl ;
    }
}

template< class TSample >
void
CovarianceCalculator< TSample >
::SetMean( MeanType* mean )
{
  const MeasurementVectorSizeType measurementVectorSize = 
    this->GetMeasurementVectorSize();

  if ( m_InternalMean != mean && m_InternalMean != 0 )
    {
    delete m_InternalMean ;
    m_InternalMean = 0 ;
    }
  
  if( mean )
    {
    const MeasurementVectorSizeType measurementVectorLength = 
      MeasurementVectorTraits::Assert( mean, measurementVectorSize,
      "Length mismatch: CovarianceCalculator::SetMean" );
    if( measurementVectorLength )
      { this->SetMeasurementVectorSize( measurementVectorLength ); }
    }

  m_Mean = mean ;

} 

template< class TSample >
typename CovarianceCalculator< TSample >::MeanType*
CovarianceCalculator< TSample >
::GetMean( void )
{
  if ( m_InternalMean != 0 )
    {
    return m_InternalMean ;
    }
  else
    {
    return m_Mean ;
    }
} 

template< class TSample >
const typename CovarianceCalculator< TSample >::OutputType*
CovarianceCalculator< TSample >
::GetOutput( void ) const
{
  return & m_Output ;
} 

template< class TSample >
inline void
CovarianceCalculator< TSample >
::ComputeCovarianceWithGivenMean( void ) 
{
  // Assert at run time that the given mean has the same length as 
  // measurement vectors in the sample and that the size is non-zero.
  MeasurementVectorTraits::Assert( m_Mean, this->GetMeasurementVectorSize(),
    "Length mismatch: CovarianceCalculator::ComputeCovarianceWithGivenMean");
  const MeasurementVectorSizeType measurementVectorSize =
                                        this->GetMeasurementVectorSize();
  
  m_Output.SetSize( measurementVectorSize, measurementVectorSize );
  m_Output.Fill(0.0);
  double frequency;
  double totalFrequency = 0.0;

  unsigned int row, col;
  unsigned int i;
  typename TSample::ConstIterator iter = this->GetInputSample()->Begin();
  typename TSample::ConstIterator end = this->GetInputSample()->End();
  MeanType diff( measurementVectorSize );
  typename TSample::MeasurementVectorType measurements;

  // fills the lower triangle and the diagonal cells in the covariance matrix
  while (iter != end)
    {
    frequency = iter.GetFrequency();
    totalFrequency += frequency;
    measurements = iter.GetMeasurementVector();
    for (i = 0 ; i < measurementVectorSize ; i++)
      {
      diff[i] = measurements[i] - (*m_Mean)[i];
      }
    for ( row = 0; row < measurementVectorSize ; row++)
      {
      for ( col = 0; col < row + 1 ; col++)
        {
        m_Output(row,col) += frequency * diff[row] * diff[col];
        }
      }
    ++iter ;
    }

  // fills the upper triangle using the lower triangle  
  for (row = 1 ; row < measurementVectorSize ; row++)
    {
    for (col = 0 ; col < row ; col++)
      {
      m_Output(col, row) = 
        m_Output(row, col);
      } 
    }
  
  if ( totalFrequency > 1e-6 )
  {
    m_Output /= ( totalFrequency - 1.0f );
  }
  else
  {
    m_Output.Fill( 0.0f );
  }

}

template< class TSample >
inline void
CovarianceCalculator< TSample >
::ComputeCovarianceWithoutGivenMean( void ) 
{
  const MeasurementVectorSizeType measurementVectorSize = 
    this->GetMeasurementVectorSize();
  m_Output.SetSize( measurementVectorSize, measurementVectorSize );
  m_Output.Fill(0.0);
  m_InternalMean = new MeanType(measurementVectorSize);
  m_InternalMean->Fill(0.0);

  double frequency;
  double totalFrequency = 0.0;

  unsigned int row, col;
  unsigned int i;
  typename TSample::ConstIterator iter = this->GetInputSample()->Begin();
  typename TSample::ConstIterator end = this->GetInputSample()->End();
  MeanType diff( measurementVectorSize );
  typename TSample::MeasurementVectorType measurements;
  //
  // fills the lower triangle and the diagonal cells in the covariance matrix
  while (iter != end)
    {
    frequency = iter.GetFrequency();
    if ( frequency == 0 )
    {
      ++iter;
      continue;
    }

    totalFrequency += frequency;
    measurements = iter.GetMeasurementVector();
    for ( i = 0 ; i < measurementVectorSize ; ++i )
      {
      diff[i] = measurements[i] - (*m_InternalMean)[i];
      }

    // updates the mean vector
    double tempWeight = frequency / totalFrequency;
    for ( i = 0 ; i < measurementVectorSize ; ++i )
      {
      (*m_InternalMean)[i] += tempWeight * diff[i];
      }

    // updates the covariance matrix
    tempWeight = tempWeight * ( totalFrequency - frequency );
    for ( row = 0; row < measurementVectorSize ; row++ )
      {
      for ( col = 0; col < row + 1 ; col++)
        {
        m_Output(row,col) += 
          tempWeight * diff[row] * diff[col];
        }
      }
    ++iter;
    }

  // fills the upper triangle using the lower triangle  
  for (row = 1 ; row < measurementVectorSize ; row++)
    {
    for (col = 0 ; col < row ; col++)
      {
      m_Output(col, row) = 
        m_Output(row, col);
      } 
    }

  if ( totalFrequency > 1e-6 )
  {
    m_Output /= ( totalFrequency - 1.0f );
  }
  else
  {
    m_Output.Fill( 0.0f );
  }

}

template< class TSample >
inline void
CovarianceCalculator< TSample >
::GenerateData() 
{
  const MeasurementVectorSizeType measurementVectorSize = 
    this->GetMeasurementVectorSize();
  if( measurementVectorSize == 0 )
    {
    itkExceptionMacro( << 
        "Measurement vector size must be set. Use SetMeasurementVectorSize( .. )");
    }

  if ( m_Mean == 0 )
    {
    this->ComputeCovarianceWithoutGivenMean();
    }
  else
    {
    this->ComputeCovarianceWithGivenMean();
    }

}


} // end of namespace Statistics 
} // end of namespace itk

#endif