mlpack  1.0.12
discrete_distribution.hpp
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1 
15 #ifndef __MLPACK_METHODS_HMM_DISTRIBUTIONS_DISCRETE_DISTRIBUTION_HPP
16 #define __MLPACK_METHODS_HMM_DISTRIBUTIONS_DISCRETE_DISTRIBUTION_HPP
17 
18 #include <mlpack/core.hpp>
19 
20 namespace mlpack {
21 namespace distribution {
22 
46 {
47  public:
51  DiscreteDistribution() { /* nothing to do */ }
52 
61  DiscreteDistribution(const size_t numObservations) :
62  probabilities(arma::ones<arma::vec>(numObservations) / numObservations)
63  { /* nothing to do */ }
64 
72  {
73  // We must be sure that our distribution is normalized.
74  double sum = accu(probabilities);
75  if (sum > 0)
76  this->probabilities = probabilities / sum;
77  else
78  {
79  this->probabilities.set_size(probabilities.n_elem);
80  this->probabilities.fill(1 / probabilities.n_elem);
81  }
82  }
83 
87  size_t Dimensionality() const { return 1; }
88 
97  double Probability(const arma::vec& observation) const
98  {
99  // Adding 0.5 helps ensure that we cast the floating point to a size_t
100  // correctly.
101  const size_t obs = size_t(observation[0] + 0.5);
102 
103  // Ensure that the observation is within the bounds.
104  if (obs >= probabilities.n_elem)
105  {
106  Log::Debug << "DiscreteDistribution::Probability(): received observation "
107  << obs << "; observation must be in [0, " << probabilities.n_elem
108  << "] for this distribution." << std::endl;
109  }
110 
111  return probabilities(obs);
112  }
113 
121  arma::vec Random() const;
122 
130  void Estimate(const arma::mat& observations);
131 
141  void Estimate(const arma::mat& observations,
142  const arma::vec& probabilities);
143 
145  const arma::vec& Probabilities() const { return probabilities; }
147  arma::vec& Probabilities() { return probabilities; }
148 
149  /*
150  * Returns a string representation of this object.
151  */
152  std::string ToString() const;
153 
154  private:
155  arma::vec probabilities;
156 };
157 
158 }; // namespace distribution
159 }; // namespace mlpack
160 
161 #endif
DiscreteDistribution(const arma::vec &probabilities)
Define the discrete distribution as having the given probabilities for each observation.
Linear algebra utility functions, generally performed on matrices or vectors.
Definition: load.hpp:23
arma::vec Random() const
Return a randomly generated observation (one-dimensional vector; one observation) according to the pr...
A discrete distribution where the only observations are discrete observations.
size_t Dimensionality() const
Get the dimensionality of the distribution.
double Probability(const arma::vec &observation) const
Return the probability of the given observation.
DiscreteDistribution()
Default constructor, which creates a distribution that has no observations.
arma::vec & Probabilities()
Modify the vector of probabilities.
static util::NullOutStream Debug
Dumps debug output into the bit nether regions.
Definition: log.hpp:76
void Estimate(const arma::mat &observations)
Estimate the probability distribution directly from the given observations.
const arma::vec & Probabilities() const
Return the vector of probabilities.
DiscreteDistribution(const size_t numObservations)
Define the discrete distribution as having numObservations possible observations. ...