MLPACK  1.0.4
discrete_distribution.hpp
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00001 
00023 #ifndef __MLPACK_METHODS_HMM_DISTRIBUTIONS_DISCRETE_DISTRIBUTION_HPP
00024 #define __MLPACK_METHODS_HMM_DISTRIBUTIONS_DISCRETE_DISTRIBUTION_HPP
00025 
00026 #include <mlpack/core.hpp>
00027 
00028 namespace mlpack {
00029 namespace distribution  {
00030 
00053 class DiscreteDistribution
00054 {
00055  public:
00059   DiscreteDistribution() { /* nothing to do */ }
00060 
00069   DiscreteDistribution(const size_t numObservations) :
00070       probabilities(arma::ones<arma::vec>(numObservations) / numObservations)
00071   { /* nothing to do */ }
00072 
00079   DiscreteDistribution(const arma::vec& probabilities)
00080   {
00081     // We must be sure that our distribution is normalized.
00082     double sum = accu(probabilities);
00083     if (sum > 0)
00084       this->probabilities = probabilities / sum;
00085     else
00086     {
00087       this->probabilities.set_size(probabilities.n_elem);
00088       this->probabilities.fill(1 / probabilities.n_elem);
00089     }
00090   }
00091 
00095   size_t Dimensionality() const { return 1; }
00096 
00105   double Probability(const arma::vec& observation) const
00106   {
00107     // Adding 0.5 helps ensure that we cast the floating point to a size_t
00108     // correctly.
00109     return probabilities((size_t) (observation[0] + 0.5));
00110   }
00111 
00119   arma::vec Random() const;
00120 
00128   void Estimate(const arma::mat& observations);
00129 
00139   void Estimate(const arma::mat& observations,
00140                 const arma::vec& probabilities);
00141 
00143   const arma::vec& Probabilities() const { return probabilities; }
00145   arma::vec& Probabilities() { return probabilities; }
00146   
00147   /*
00148    * Returns a string representation of this object.
00149    */
00150   std::string ToString() const;
00151 
00152  private:
00153   arma::vec probabilities;
00154 };
00155 
00156 }; // namespace distribution
00157 }; // namespace mlpack
00158 
00159 #endif