SphinxExamples/src/Numerics/Statistics/HistogramCreationAndBinAccess/Code.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.
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 *=========================================================================*/
 
#include "itkHistogram.h"
#include "itkDenseFrequencyContainer2.h"
 
int
main()
{
  using MeasurementType = float;
  using FrequencyContainerType = itk::Statistics::DenseFrequencyContainer2;
 
  constexpr unsigned int numberOfComponents = 2;
  using HistogramType = itk::Statistics::Histogram<MeasurementType, FrequencyContainerType>;
 
  auto histogram = HistogramType::New();
  histogram->SetMeasurementVectorSize(numberOfComponents);
 
  // We initialize it as a 3x3 histogram with equal size intervals.
 
  HistogramType::SizeType size(numberOfComponents);
  size.Fill(3);
  HistogramType::MeasurementVectorType lowerBound(numberOfComponents);
  HistogramType::MeasurementVectorType upperBound(numberOfComponents);
  lowerBound[0] = 1.1;
  lowerBound[1] = 2.6;
  upperBound[0] = 7.1;
  upperBound[1] = 8.6;
 
  histogram->Initialize(size, lowerBound, upperBound);
 
  // Now the histogram is ready for storing frequency values. There
  // are three ways of accessing data elements in the histogram:
  // - using instance identifiers---just like any other Sample object;
  // - using n-dimensional indices---just like an Image object;
  // - using an iterator---just like any other Sample object.
  //
  // In this example, the index (0, 0) refers the same bin as the instance
  // identifier (0) refers to. The instance identifier of the index (0,
  // 1) is (3), (0, 2) is (6), (2, 2) is (8), and so on.
 
  histogram->SetFrequency(0, 0);
  histogram->SetFrequency(1, 2);
  histogram->SetFrequency(2, 3);
  histogram->SetFrequency(3, 2);
  histogram->SetFrequency(4, 1);
  histogram->SetFrequency(5, 1);
  histogram->SetFrequency(6, 5);
  histogram->SetFrequency(7, 4);
  histogram->SetFrequency(8, 0);
 
  // Let us examine if the frequency is set correctly by calling the
  // GetFrequency(index) method. We can use the
  // GetFrequency(instance identifier) method for the same purpose.
 
  HistogramType::IndexType index(numberOfComponents);
  index[0] = 0;
  index[1] = 2;
  std::cout << "Frequency of the bin at index " << index << " is " << histogram->GetFrequency(index)
            << " and the bin's instance identifier is " << histogram->GetInstanceIdentifier(index) << std::endl;
 
  return EXIT_SUCCESS;
}