PCAStatistics

#include <vtkSmartPointer.h>
#include <vtkDoubleArray.h>
#include <vtkMultiBlockDataSet.h>
#include <vtkPCAStatistics.h>
#include <vtkStringArray.h>
#include <vtkTable.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();
  pcaStatistics->SetInputData( vtkStatisticsAlgorithm::INPUT_DATA, datasetTable );
  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;
}

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(PCAStatistics)

find_package(VTK COMPONENTS 
  vtkvtkCommonCore
  vtkvtkCommonDataModel
  vtkvtkFiltersStatistics QUIET)
if (NOT VTK_FOUND)
  message("Skipping PCAStatistics: ${VTK_NOT_FOUND_MESSAGE}")
  return ()
endif()
message (STATUS "VTK_VERSION: ${VTK_VERSION}")
if (VTK_VERSION VERSION_LESS "8.90.0")
  # old system
  include(${VTK_USE_FILE})
  add_executable(PCAStatistics MACOSX_BUNDLE PCAStatistics.cxx )
  target_link_libraries(PCAStatistics PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(PCAStatistics MACOSX_BUNDLE PCAStatistics.cxx )
  target_link_libraries(PCAStatistics PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS PCAStatistics
    MODULES ${VTK_LIBRARIES}
    )
endif ()

cd PCAStatistics/build

cmake ..

cmake -DVTK_DIR:PATH=/home/me/vtk_build ..

make

./PCAStatistics