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HiddenMarkovModel


abstract class HiddenMarkovModel<Parameter, State, Observation> < MarkovModel<Parameter, State>

Hidden Markov Model (HMM). Synonymous with StateSpaceModel.

classDiagram Model <|-- MarkovModel MarkovModel <|-- HiddenMarkovModel HiddenMarkovModel -- StateSpaceModel link Model "../Model/" link MarkovModel "../MarkovModel/" link HiddenMarkovModel "../HiddenMarkovModel/" link StateSpaceModel "../StateSpaceModel/"

The joint distribution is:

\underbrace{p(\mathrm{d}\theta, \mathrm{d}x_{1:T}, \mathrm{d}y_{1:T})}_{\text{joint}} = \underbrace{p(\mathrm{d}\theta)}_{\text{parameter}} \underbrace{p(\mathrm{d}x_1 \mid \theta)}_{\text{initial}} \left(\prod_{t=2}^T \underbrace{p(\mathrm{d}x_t \mid x_{t-1}, \theta)}_{\text{transition}} \right) \left(\prod_{t=1}^T \underbrace{p(\mathrm{d}y_t \mid x_t, \theta)}_{\text{observation}}. \right).

Typically the \theta and x_{0:T} are latent, while the y_{0:T} are observed; this is the classic hidden Markov model (HMM) or state-space model (SSM). In this implementation, however, any variables may be latent or observed.

A model derived from HiddenMarkovModel overrides the parameter(), initial(), transition() and observation() member functions to specify the individual components of the joint distribution. The HiddenMarkovModel class itself overrides the simulate() and simulate(t) member functions of Model to call these more specific functions internally.

Member Variables

Name Description
y:Tape<Observation> Observations.

Member Functions

Name Description
observation Observation model.

Member Function Details

observation

function observation(y:Observation, x:State, θ:Parameter)

Observation model.

  • y: The observations, to be set.
  • x: The current state.
  • θ: The parameters.