LeastSquares
VTKExamples/Cxx/Math/LeastSquares
Description¶
This example solves XM = Y (an interesting way to write Ax = b).
In particular, we are trying to solve
[4] [-2](1) [2] M = [6](1) [3] [1](2)
It currently does not work.
Code¶
LeastSquares.cxx
#include <vtkSmartPointer.h> #include <vtkMath.h> /* 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; } 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] = 4; x[1][0] = 1; x[1][1] = 2; x[2][0] = 2; x[2][1] = 3; double **m = create_matrix<double> ( numberOfVariables, 1 ); double **y = create_matrix<double> ( numberOfSamples, 1 ); y[0][0] = -2; y[1][0] = 6; y[2][0] = 1; vtkMath::SolveLeastSquares(numberOfSamples, x, numberOfVariables, y, 1, m); std::cout << "Solution is: " << m[0][0] << " " << m[1][0] << std::endl; // Solution should be [3; -1]; free_matrix(x); free_matrix(m); free_matrix(y); return EXIT_SUCCESS; }
CMakeLists.txt¶
cmake_minimum_required(VERSION 2.8) PROJECT(LeastSquares) find_package(VTK REQUIRED) include(${VTK_USE_FILE}) add_executable(LeastSquares MACOSX_BUNDLE LeastSquares.cxx) target_link_libraries(LeastSquares ${VTK_LIBRARIES})
Download and Build LeastSquares¶
Danger
The generation of tar files has not been ported to the new VTKExamples. Some tarballs may be missing or out-of-date.
Click here to download LeastSquares and its CMakeLists.txt file. Once the tarball LeastSquares.tar has been downloaded and extracted,
cd LeastSquares/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:
./LeastSquares
WINDOWS USERS PLEASE NOTE: Be sure to add the VTK bin directory to your path. This will resolve the VTK dll's at run time.