root/library/bdm/estim/arx.h @ 679

/*!
  \file
  \brief Bayesian Filtering for generalized autoregressive (ARX) model
  \author Vaclav Smidl.

  -----------------------------------
  BDM++ - C++ library for Bayesian Decision Making under Uncertainty

  Using IT++ for numerical operations
  -----------------------------------
*/

#ifndef AR_H
#define AR_H

#include "../math/functions.h"
#include "../stat/exp_family.h"
#include "../base/user_info.h"
//#include "../estim/kalman.h"
#include "arx_straux.h"

namespace bdm {

/*!
* \brief Linear Autoregressive model with Gaussian noise

Regression of the following kind:
\f[
y_t = \theta_1 \psi_1 + \theta_2 + \psi_2 +\ldots + \theta_n \psi_n + r e_t
\f]
where unknown parameters \c rv are \f$[\theta r]\f$, regression vector \f$\psi=\psi(y_{1:t},u_{1:t})\f$ is a known function of past outputs and exogeneous variables \f$u_t\f$. Distrubances \f$e_t\f$ are supposed to be normally distributed:
\f[
e_t \sim \mathcal{N}(0,1).
\f]

See \ref tut_arx for mathematical treatment.

The easiest way how to use the class is:
\include arx_simple.cpp

        \todo sort out constant terms - bayes should accept vec without additional 1s
*/
class ARX: public BMEF {
protected:
        //! switch if constant is modelled or not
        bool have_constant;
        //! vector of dyadic update
        vec dyad;
        //! posterior density
        egiw est;
        //! Alternative estimate of parameters, used in stabilized forgetting, see [Kulhavy]
        egiw alter_est;
public:
        //! \name Constructors
        //!@{
        ARX ( const double frg0 = 1.0 ) : BMEF ( frg0 ),  have_constant(true), dyad(), est() {};
        ARX ( const ARX &A0 ) : BMEF (A0.frg),  have_constant(A0.have_constant), dyad(A0.dyad),est(est) { };
        ARX* _copy_() const;
        void set_parameters ( double frg0 ) {
                frg = frg0;
        }
        void set_constant ( bool const0 ) {
                have_constant=const0;
        }
        void set_statistics ( int dimy0, const ldmat V0, double nu0 = -1.0 ) {
                est.set_parameters ( dimy0, V0, nu0 );
                last_lognc = est.lognc();
                dimy = dimy0;
        }
        //!@}

        //! Set sufficient statistics
        void set_statistics ( const BMEF* BM0 );

        //!\name Mathematical operations
        //!@{

        //! Weighted Bayes \f$ dt = [y_t psi_t] \f$.
        void bayes_weighted ( const vec &yt, const vec &cond=empty_vec, const double w=1.0 );
        void bayes( const vec &yt, const vec &cond=empty_vec ) {
                bayes_weighted ( yt,cond, 1.0 );
        };
        double logpred ( const vec &yt ) const;
        void flatten ( const BMEF* B ) {
                const ARX* A = dynamic_cast<const ARX*> ( B );
                // nu should be equal to B.nu
                est.pow ( A->posterior()._nu() / posterior()._nu() );
                if ( evalll ) {
                        last_lognc = est.lognc();
                }
        }
        //! Conditioned version of the predictor
        enorm<ldmat>* epredictor ( const vec &rgr ) const;
        //! Predictor for empty regressor
        enorm<ldmat>* epredictor() const {
                bdm_assert_debug ( dimy == posterior()._V().rows() - 1, "Regressor is not only 1" );
                return epredictor ( vec_1 ( 1.0 ) );
        }
        //! conditional version of the predictor
        mlnorm<ldmat>* predictor() const;
        mlstudent* predictor_student() const;
        //! Brute force structure estimation.\return indeces of accepted regressors.
        ivec structure_est ( egiw Eg0 );
        //! Smarter structure estimation by Ludvik Tesar.\return indeces of accepted regressors.
        ivec structure_est_LT ( egiw Eg0 );
        //!@}

        //!\name Access attributes
        //!@{
                //! return correctly typed posterior (covariant return)
                const egiw& posterior() const {
                return est;
        }
        //!@}

        /*! UI for ARX estimator

        \code
        class = 'ARX';
        rv    = RV({names_of_dt} )                 // description of output variables
        rgr   = RV({names_of_regressors}, [-1,-2]} // description of regressor variables
        constant = 1;                              // 0/1 switch if the constant term is modelled or not

        --- optional ---
        prior = {class='egiw',...};                // Prior density, when given default is used instead
        alternative = {class='egiw',...};          // Alternative density in stabilized estimation, when not given prior is used
        
        frg = 1.0;                                 // forgetting, default frg=1.0

        rv_param   = RV({names_of_parameters}}     // description of parametetr names 
                                                                                           // default: ["theta_i" and "r_i"]
        \endcode
        */
        void from_setting ( const Setting &set );

        void validate() {
                //if dimc not set set it from V
                if (dimc==0){
                        dimc = posterior()._V().rows()-dimy-int(have_constant==true);
                }
                        
                if (have_constant) {
                        dyad = ones(dimy+dimc+1);
                } else { 
                        dyad = zeros(dimy+dimc);
                }
                        
        }
        //! function sets prior and alternative density 
        void set_prior(const RV &drv, egiw &prior){
                //TODO check ranges in RV and build prior
        };
        //! build default prior and alternative when all values are set
        void set_prior_default(egiw &prior){
                //assume 
                vec dV0(prior._V().rows());
                dV0.set_subvector(0,prior._dimx()-1, 1.0);
                dV0.set_subvector(prior._dimx(),dV0.length()-1, 1e-5);
                
                prior.set_parameters(prior._dimx(),ldmat(dV0));
        }
};

UIREGISTER ( ARX );
SHAREDPTR ( ARX );

/*! ARX model conditined by knowledge of the forgetting factor
\f[ f(\theta| d_1 \ldots d_t , \phi_t) \f]
*/
class ARXfrg : public ARX{
        public:
                ARXfrg():ARX(){};
                //! copy constructor
                ARXfrg(const ARXfrg &A0):ARX(A0){};
                ARXfrg* _copy_() const {ARXfrg *A = new ARXfrg(*this); return A;}
        void condition(const vec &val){
                frg = val(0);
        }
};
UIREGISTER(ARXfrg);
};
#endif // AR_H