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HomogeneousLeastSquares

vtk-examples/Cxx/Math/HomogeneousLeastSquares

Question

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Code

HomogeneousLeastSquares.cxx

#include <vtkMath.h>

namespace {
/* allocate memory for an nrow x ncol matrix */
template <class TReal> TReal** create_matrix(long nrow, long ncol)
{
  typedef TReal* TRealPointer;
  TReal** m = new TRealPointer[nrow];

  TReal* block = (TReal*)calloc(nrow * ncol, sizeof(TReal));
  m[0] = block;
  for (int row = 1; row < nrow; ++row)
  {
    m[row] = &block[row * ncol];
  }
  return m;
}

/* free a TReal matrix allocated with matrix() */
template <class TReal> void free_matrix(TReal** m)
{
  free(m[0]);
  delete[] m;
}

} // namespace

int main(int, char*[])
{

  // Solve XM = Y;

  int numberOfSamples = 3;
  int numberOfVariables = 2;
  double** x = create_matrix<double>(numberOfSamples, numberOfVariables);
  x[0][0] = 1;
  x[0][1] = 2;
  x[1][0] = 2;
  x[1][1] = 4;
  x[2][0] = 3;
  x[2][1] = 6;

  double** m = create_matrix<double>(numberOfVariables, 1);

  vtkMath::SolveHomogeneousLeastSquares(numberOfSamples, x, numberOfVariables,
                                        m);

  std::cout << "Solution is: " << m[0][0] << " " << m[1][0] << std::endl;

  free_matrix(x);
  free_matrix(m);

  return EXIT_SUCCESS;
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.3 FATAL_ERROR)

project(HomogeneousLeastSquares)

find_package(VTK COMPONENTS 
  vtkCommonCore
  QUIET
)

if (NOT VTK_FOUND)
  message("Skipping HomogeneousLeastSquares: ${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(HomogeneousLeastSquares MACOSX_BUNDLE HomogeneousLeastSquares.cxx )
  target_link_libraries(HomogeneousLeastSquares PRIVATE ${VTK_LIBRARIES})
else ()
  # include all components
  add_executable(HomogeneousLeastSquares MACOSX_BUNDLE HomogeneousLeastSquares.cxx )
  target_link_libraries(HomogeneousLeastSquares PRIVATE ${VTK_LIBRARIES})
  # vtk_module_autoinit is needed
  vtk_module_autoinit(
    TARGETS HomogeneousLeastSquares
    MODULES ${VTK_LIBRARIES}
    )
endif ()

Download and Build HomogeneousLeastSquares

Click here to download HomogeneousLeastSquares and its CMakeLists.txt file. Once the tarball HomogeneousLeastSquares.tar has been downloaded and extracted,

cd HomogeneousLeastSquares/build

If VTK is installed:

cmake ..

If VTK is not installed but compiled on your system, you will need to specify the path to your VTK build:

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

Build the project:

make

and run it:

./HomogeneousLeastSquares

WINDOWS USERS

Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.