Examples/Statistics/NeighborhoodSampler.cxx

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// Software Guide : BeginLatex
//
// \index{Statistics!Sampling measurement vectors using radius}
// \index{itk::Statistics::NeighborhoodSampler}
//
// When we want to create an \subdoxygen{Statistics}{Subsample} object that
// includes only the measurement vectors within a radius from a center in a
// sample, we can use the \subdoxygen{Statistics}{NeighborhoodSampler}. In this
// example, we will use the \subdoxygen{Statistics}{ListSample} as the input
// sample.
//
// We include the header files for the ListSample and the
// NeighborhoodSampler classes.
//
// Software Guide : EndLatex


// Software Guide : BeginCodeSnippet
#include "itkListSample.h"
#include "itkNeighborhoodSampler.h"
// Software Guide : EndCodeSnippet

// Software Guide : BeginLatex
//
// We need another header for measurement vectors. We are going to use the
// \doxygen{Vector} class which is a subclass of the \doxygen{FixedArray}.
//
// Software Guide : EndLatex

// Software Guide : BeginCodeSnippet
#include "itkVector.h"
// Software Guide : EndCodeSnippet

int main()
{
  // Software Guide : BeginLatex
  //
  // The following code snippet will create a ListSample object
  // with two-component int measurement vectors and put the measurement
  // vectors: [1,1] - 1 time, [2,2] - 2 times, [3,3] - 3 times, [4,4] -
  // 4 times, [5,5] - 5 times into the \code{listSample}.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using MeasurementType = int;
  constexpr unsigned int MeasurementVectorLength = 2;
  using MeasurementVectorType =
      itk::Vector< MeasurementType , MeasurementVectorLength >;
  using SampleType = itk::Statistics::ListSample< MeasurementVectorType >;
  SampleType::Pointer sample = SampleType::New();
  sample->SetMeasurementVectorSize( MeasurementVectorLength );

  MeasurementVectorType mv;
  for (unsigned int i = 1; i < 6; ++i)
    {
    for (unsigned int j = 0; j < 2; ++j)
      {
      mv[j] = ( MeasurementType ) i;
      }
    for (unsigned int j = 0; j < i; ++j)
      {
      sample->PushBack(mv);
      }
    }
  // Software Guide : EndCodeSnippet

  // Software Guide : BeginLatex
  //
  // We plug-in the sample to the NeighborhoodSampler using the
  // \code{SetInputSample(sample*)}. The two required inputs for the
  // NeighborhoodSampler are a center and a radius. We set these two inputs
  // using the \code{SetCenter(center vector*)} and the
  // \code{SetRadius(double*)} methods respectively. And then we call the
  // \code{Update()} method to generate the Subsample object. This
  // sampling procedure subsamples measurement vectors within a
  // hyper-spherical kernel that has the center and radius specified.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  using SamplerType = itk::Statistics::NeighborhoodSampler< SampleType >;
  SamplerType::Pointer sampler = SamplerType::New();

  sampler->SetInputSample( sample );
  SamplerType::CenterType center( MeasurementVectorLength );
  center[0] = 3;
  center[1] = 3;
  double radius = 1.5;
  sampler->SetCenter( &center );
  sampler->SetRadius( &radius );
  sampler->Update();

  SamplerType::OutputType::Pointer output = sampler->GetOutput();
  // Software Guide : EndCodeSnippet


  // Software Guide : BeginLatex
  //
  // The \code{SamplerType::OutputType} is in fact
  // \subdoxygen{Statistics}{Subsample}. The following code prints out
  // the resampled measurement vectors.
  //
  // Software Guide : EndLatex

  // Software Guide : BeginCodeSnippet
  SamplerType::OutputType::Iterator iter = output->Begin();
  while ( iter != output->End() )
    {
    std::cout << "instance identifier = " << iter.GetInstanceIdentifier()
              << "\t measurement vector = "
              << iter.GetMeasurementVector()
              << "\t frequency = "
              << iter.GetFrequency() << std::endl;
    ++iter;
    }
  // Software Guide : EndCodeSnippet

  return EXIT_SUCCESS;

}