/// <summary>
/// Learns the transition probabilities from the specified training set.
/// </summary>
/// <param name="transition">The transition matrix.</param>
/// <param name="trainingSet">The training set.</param>
private void Learn([NotNull] TransitionMatrix transition, [NotNull] IEnumerable <IList <LabeledObservation> > trainingSet)
{
// generate bigrams from each training sentence and
// group these pairs by the left item's state
var pairsGroupedByLeftState = trainingSet
.SelectMany(set => set.Pairwise())
.GroupBy(pair => pair.Left.State);
// for each left state, group the items by the right states
foreach (var pairsOfSameStartingClass in pairsGroupedByLeftState)
{
var leftState = pairsOfSameStartingClass.Key;
var pairsOfSameStartingStateGroupedByRightState =
pairsOfSameStartingClass.GroupBy(pair => pair.Right.State);
var countOfSameStartingState = pairsOfSameStartingClass.Count();
// determine each probability P(left -> right) by dividing
// the occurrence count of each right state by the total number of all
// occurrences starting in the left state
foreach (var grouping in pairsOfSameStartingStateGroupedByRightState)
{
var rightState = grouping.Key;
var occurrences = grouping.Count();
var percentage = (double)occurrences / countOfSameStartingState;
transition.SetTransition(leftState, rightState, percentage);
}
}
}
/// <summary>
/// Learns the parameters for the given system.
/// </summary>
/// <param name="initial">The initial.</param>
/// <param name="transition">The transition.</param>
/// <param name="emission">The emission.</param>
/// <param name="trainingSet">The training set.</param>
public void Learn([NotNull] InitialStateMatrix initial, [NotNull] TransitionMatrix transition,
[NotNull] EmissionMatrix emission,
[NotNull] IList <IList <LabeledObservation> > trainingSet)
{
Learn(initial, trainingSet);
Learn(transition, trainingSet);
Learn(emission, trainingSet);
}
/// <summary>
/// Initializes a new instance of the <see cref="HiddenMarkovModel" /> class.
/// </summary>
/// <param name="states">The states.</param>
/// <param name="inital">The inital state matrix.</param>
/// <param name="transition">The transmission matrix.</param>
/// <param name="emission">The emission matrix.</param>
public HiddenMarkovModel(
[NotNull] ReadOnlyCollection <IState> states,
[NotNull] InitialStateMatrix inital,
[NotNull] TransitionMatrix transition,
[NotNull] EmissionMatrix emission)
{
_states = states;
_inital = inital;
_transition = transition;
_emission = emission;
}
