classification/LeftToRightHMM.h

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#ifndef _LEFTTORIGHTHMM_H
#define _LEFTTORIGHTHMM_H
#include <vector>
#include "../util/Matrix.h"


class LeftToRightHMM 
{
    public:
        typedef std::vector<int> Observation;

        LeftToRightHMM(size_t nStates, size_t alphabetSize);

        double evaluate(Observation &obs);

        void train(Observation &obs, size_t maxIterations);

        const size_t getStateCount() const { return m_nStates; }

        Matrix<double> &getTransitionProps() { return m_transitionProps; }

        Matrix<double> &getOutputProps() { return m_outputProps; }

        void setTransitionProps(const Matrix<double> &matrix) { m_transitionProps = matrix; }

        void setOutputProps(const Matrix<double> &matrix) { m_outputProps = matrix; }

    private:
        void adjustParameters(Observation &obs, std::vector<Matrix<double> > &xi);
        void calcXi(Observation &obs, Matrix<double> &alpha,
                Matrix<double> &beta, std::vector<Matrix<double> > &xi);
        Matrix<double> &forwardTrelis(Observation &obs);

        Matrix<double> &backwardTrelis(Observation &obs);

        size_t m_nStates;
        Matrix<double> m_transitionProps;
        Matrix<double> m_outputProps;
        Matrix<double> m_trelis;
};

#endif

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