VTK/Examples/Cxx/Utilities/vtkPCAStatistics

#include <vtkVersion.h>
#include "vtkSmartPointer.h"
#include "vtkDoubleArray.h"
#include "vtkMultiBlockDataSet.h"
#include "vtkPCAStatistics.h"
#include "vtkStringArray.h"
#include "vtkTable.h"
#include "vtkTestUtilities.h"
 
int main(int, char*[])
{
  // Each one of these arrays is a single component of
  // the data. That is, if you have 3D spatial data (x,y,z)
  // you need to construct an array of all the x values,
  // an array of all the y values, and an array of all the
  // z values.
 
  // Construct a data set of 3 3D points.
 
  // These would be all of your "x" values.
  const char m0Name[] = "M0";
  vtkSmartPointer<vtkDoubleArray> dataset1Arr =
    vtkSmartPointer<vtkDoubleArray>::New();
  dataset1Arr->SetNumberOfComponents(1);
  dataset1Arr->SetName( m0Name );
  dataset1Arr->InsertNextValue(0);
  dataset1Arr->InsertNextValue(1);
  dataset1Arr->InsertNextValue(0);
 
  // These would be all of your "y" values.
  const char m1Name[] = "M1";
  vtkSmartPointer<vtkDoubleArray> dataset2Arr =
    vtkSmartPointer<vtkDoubleArray>::New();
  dataset2Arr->SetNumberOfComponents(1);
  dataset2Arr->SetName( m1Name );
  dataset2Arr->InsertNextValue(0);
  dataset2Arr->InsertNextValue(0);
  dataset2Arr->InsertNextValue(1);
 
  // These would be all of your "z" values.
  const char m2Name[] = "M2";
  vtkSmartPointer<vtkDoubleArray> dataset3Arr =
    vtkSmartPointer<vtkDoubleArray>::New();
  dataset3Arr->SetNumberOfComponents(1);
  dataset3Arr->SetName( m2Name );
  dataset3Arr->InsertNextValue(0);
  dataset3Arr->InsertNextValue(0);
  dataset3Arr->InsertNextValue(0);
 
  vtkSmartPointer<vtkTable> datasetTable =
    vtkSmartPointer<vtkTable>::New();
  datasetTable->AddColumn(dataset1Arr);
  datasetTable->AddColumn(dataset2Arr);
  datasetTable->AddColumn(dataset3Arr);
 
  vtkSmartPointer<vtkPCAStatistics> pcaStatistics =
    vtkSmartPointer<vtkPCAStatistics>::New();
#if VTK_MAJOR_VERSION <= 5
  pcaStatistics->SetInput( vtkStatisticsAlgorithm::INPUT_DATA, datasetTable );
#else
  pcaStatistics->SetInputData( vtkStatisticsAlgorithm::INPUT_DATA, datasetTable );
#endif
 
  pcaStatistics->SetColumnStatus("M0", 1 );
  pcaStatistics->SetColumnStatus("M1", 1 );
  pcaStatistics->SetColumnStatus("M2", 1 );
  pcaStatistics->RequestSelectedColumns();
  pcaStatistics->SetDeriveOption(true);
  pcaStatistics->Update();
 
  ///////// Eigenvalues ////////////
  vtkSmartPointer<vtkDoubleArray> eigenvalues =
    vtkSmartPointer<vtkDoubleArray>::New();
  pcaStatistics->GetEigenvalues(eigenvalues);
  double eigenvaluesGroundTruth[3] = {.5, .166667, 0};
  for(vtkIdType i = 0; i < eigenvalues->GetNumberOfTuples(); i++)
    {
    std::cout << "Eigenvalue " << i << " = " << eigenvalues->GetValue(i) << std::endl;
    }
 
  ///////// Eigenvectors ////////////
  vtkSmartPointer<vtkDoubleArray> eigenvectors =
    vtkSmartPointer<vtkDoubleArray>::New();
 
  pcaStatistics->GetEigenvectors(eigenvectors);
  for(vtkIdType i = 0; i < eigenvectors->GetNumberOfTuples(); i++)
    {
    std::cout << "Eigenvector " << i << " : ";
    double* evec = new double[eigenvectors->GetNumberOfComponents()];
    eigenvectors->GetTuple(i, evec);
    for(vtkIdType j = 0; j < eigenvectors->GetNumberOfComponents(); j++)
      {
      std::cout << evec[j] << " ";
      vtkSmartPointer<vtkDoubleArray> eigenvectorSingle =
        vtkSmartPointer<vtkDoubleArray>::New();
      pcaStatistics->GetEigenvector(i, eigenvectorSingle);
      }
    delete evec;
    std::cout << std::endl;
    }
 
  return EXIT_SUCCESS;
}