diff --git a/doc/dynare.texi b/doc/dynare.texi index 611683734..bafb4438a 100644 --- a/doc/dynare.texi +++ b/doc/dynare.texi @@ -2875,7 +2875,8 @@ The simulated endogenous variables are available in global matrix @defvr {MATLAB/Octave variable} oo_.endo_simul This variable stores the result of a deterministic simulation (computed by @code{simul}) or of a stochastic simulation (computed by -@code{stoch_simul} with the @code{periods} option). +@code{stoch_simul} with the @code{periods} option or by +@code{extended_path}). The variables are arranged row by row, in order of declaration (as in @code{M_.endo_names}). Note that this variable also contains initial @@ -2883,16 +2884,38 @@ and terminal conditions, so it has more columns than the value of @code{periods} option. @end defvr +@anchor{oo_.exo_simul} +@defvr {MATLAB/Octave variable} oo_.exo_simul +This variable stores the path of exogenous variables during a +simulation (computed by @code{simul}, @code{stoch_simul} or +@code{extended_path}). + +The variables are arranged in columns, in order of declaration (as in +@code{M_.endo_names}). Periods are in rows. Note that this convention +regarding columns and rows is the opposite of the convention for +@code{oo_.endo_simul}! + +@end defvr + @node Stochastic solution and simulation @section Stochastic solution and simulation In a stochastic context, Dynare computes one or several simulations -corresponding to a random draw of the shocks. Dynare uses a Taylor +corresponding to a random draw of the shocks. + +The main algorithm for solving stochastic models relies on a Taylor approximation, up to third order, of the expectation functions (see @cite{Judd (1996)}, @cite{Collard and Juillard (2001a)}, @cite{Collard and Juillard (2001b)}, and @cite{Schmitt-Grohé and Uríbe (2004)}). The details of the Dynare implementation of the first order solution are -given in @cite{Villemot (2011)}. +given in @cite{Villemot (2011)}. Such a solution is computed using +the @code{stoch_simul} command. + +As an alternative, it is possible to compute a simulation to a +stochastic model using the @emph{extended path} method presented by +@cite{Fair and Taylor (1983)}. This method is especially useful when +there are strong nonlinearities or binding constraints. Such a +solution is computed using the @code{extended_path} command. @menu * Computing the stochastic solution:: @@ -3052,7 +3075,9 @@ periods to use in the simulations. Values of the @code{initval} block, possibly recomputed by @code{steady}, will be used as starting point for the simulation. The simulated endogenous variables are made available to the user in a vector for each variable and in the global -matrix @code{oo_.endo_simul} (@pxref{oo_.endo_simul}). Default: @code{0}. +matrix @code{oo_.endo_simul} (@pxref{oo_.endo_simul}). The simulated +exogenous variables are made available in @code{oo_.exo_simul} +(@pxref{oo_.exo_simul}). Default: @code{0}. @item qz_criterium = @var{DOUBLE} Value used to split stable from unstable eigenvalues in reordering the @@ -3250,6 +3275,37 @@ variables of the model as function of the previous state of the model and shocks oberved at the beginning of the period. The decision rules are stored in the structure @code{oo_.dr} which is described below. +@deffn Command extended_path ; +@deffnx Command extended_path (@var{OPTIONS}@dots{}) ; + +@descriptionhead + +@code{extended_path} solves a stochastic (@i{i.e.} rational +expectations) model, using the @emph{extended path} method presented +by @cite{Fair and Taylor (1983)}. + +This function first computes a random path for the exogenous variables +(stored in @code{oo_.exo_simul}, @pxref{oo_.exo_simul}) and then +computes the corresponding path for endogenous variables, taking the +steady state as starting point. The result of the simulation is stored +in @code{oo_.endo_simul} (@pxref{oo_.endo_simul}). + +@optionshead + +@table @code + +@item periods = @var{INTEGER} +The number of periods for which the simulation is to be computed. No +default value, mandatory option. + +@item solver_periods = @var{INTEGER} +The number of periods used to compute the approximate solution +at every iteration of the algorithm. Default: @code{200}. + +@end table + +@end deffn + @node Typology and ordering of variables @subsection Typology and ordering of variables