MathHelper.cpp

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#include "helper/MathHelper.h"
#include <random>

namespace ProbabilisticSceneRecognition {
 
  MathHelper::MathHelper()
  {
  }
  
  MathHelper::~MathHelper()
  {
  }

  void MathHelper::drawNormal(const Eigen::VectorXd& mean, const Eigen::MatrixXd& cov, unsigned int amount, std::vector<Eigen::VectorXd>& samples)
  {
      Eigen::SelfAdjointEigenSolver<Eigen::MatrixXd> solver(cov);
      Eigen::MatrixXd t = solver.eigenvectors() * solver.eigenvalues().cwiseSqrt().asDiagonal();
      std::default_random_engine generator(0);  // set fixed seed so the same data gets plotted the same way every time
      std::normal_distribution<double> distr;
      samples.resize(amount);
      for (unsigned int i = 0; i < amount; i++) {
          Eigen::VectorXd randomvect(mean.size());
          for (unsigned int i = 0; i < randomvect.size(); i++) randomvect[i] = distr(generator);
          samples.at(i) = mean + t * randomvect;
      }
  }

  void MathHelper::calcHistogram(double lower, double upper, unsigned int buckets, std::vector<double> in, std::vector<std::pair<double, double>>& out)
  {
      out.resize(buckets);
      double range = std::abs(lower) + std::abs(upper);
      double bucketsize = range / buckets;

      for (unsigned int i = 0; i < buckets; i++)
      {
          out.at(i).first = lower + (i * bucketsize);
          out.at(i).second = 0;
      }
      for (double sample: in)
      {
          if (lower <= sample && sample <= upper) {
              unsigned int bucket = ((double) (sample - lower)) / bucketsize;
              if (0 <= bucket && bucket < buckets) out.at(bucket).second++;
          }
      }
  }
  
}