Example: math_kmeans_example

C++ example source code:

/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2024, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include <mrpt/gui/CDisplayWindowPlots.h>
#include <mrpt/math/CVectorFixed.h>
#include <mrpt/math/TPoint2D.h>
#include <mrpt/math/kmeans.h>
#include <mrpt/random.h>
#include <mrpt/system/CTicTac.h>

#include <iostream>
#include <vector>

using namespace mrpt::math;
using namespace mrpt::gui;
using namespace mrpt::random;
using namespace mrpt::system;
using namespace std;

// ------------------------------------------------------
//              TestKMeans
// ------------------------------------------------------
void TestKMeans()
{
  typedef CVectorFixedDouble<2> CPointType;
  // typedef CVectorFixedFloat<2>  CPointType;

  getRandomGenerator().randomize();
  CTicTac tictac;

  CDisplayWindowPlots win("k-means results");

  cout << "Close the window to end.\n";

  while (win.isOpen())
  {
    // Generate N clusters of random points:
    std::vector<CPointType> points;
    const size_t nClusters = 2 + (getRandomGenerator().drawUniform32bit() % 4);

    for (size_t cl = 0; cl < nClusters; cl++)
    {
      const size_t nPts = getRandomGenerator().drawUniform<size_t>(5, 50);

      TPoint2D clCenter;
      clCenter.x = getRandomGenerator().drawUniform(0, 10);
      clCenter.y = getRandomGenerator().drawUniform(0, 10);

      for (size_t p = 0; p < nPts; p++)
      {
        CPointType v;
        v[0] = clCenter.x + getRandomGenerator().drawGaussian1D(0, 1);
        v[1] = clCenter.y + getRandomGenerator().drawGaussian1D(0, 1);
        points.push_back(v);
      }
    }

    // do k-means
    std::vector<CPointType> centers;
    vector<int> assignments;
    tictac.Tic();

    const double cost = mrpt::math::kmeanspp(nClusters, points, assignments, &centers);

    cout << "Took: " << tictac.Tac() * 1e3 << " ms.\n";
    cout << "cost: " << cost << endl;

    // Show:
    win.clf();
    win.hold_on();
    static const char colors[6] = {'b', 'r', 'k', 'g', 'm', 'c'};

    for (size_t c = 0; c < nClusters; c++)
    {
      CVectorDouble xs, ys;

      for (size_t i = 0; i < points.size(); i++)
      {
        if (size_t(assignments[i]) == c)
        {
          xs.push_back(points[i][0]);
          ys.push_back(points[i][1]);
        }
      }
      win.plot(xs, ys, mrpt::format(".4%c", colors[c % 6]));
    }
    win.axis_fit();
    win.axis_equal();

    cout << "Press any key to generate another random dataset...\n";
    win.waitForKey();
  };
}

int main(int argc, char** argv)
{
  try
  {
    TestKMeans();
    return 0;
  }
  catch (const std::exception& e)
  {
    std::cerr << "MRPT error: " << mrpt::exception_to_str(e) << std::endl;
    return -1;
  }
  catch (...)
  {
    printf("Another exception!!");
    return -1;
  }
}