Examples/Statistics/NeighborhoodSampler.cxx

/*=========================================================================
 *
 *  Copyright NumFOCUS
 *
 *  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
 *
 *         https://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.
 *
 *=========================================================================*/
 
// 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>;
  auto 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>;
  auto 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;
}