Overview of model source language

The model source language is used to describe all the elements of a model in human-readable form: variables, parameters, shocks, equations, etc. The model source is then translated to a structural model object.

Slang is a set of keywords that define the structure of model source files. The model source files are plain text files (saved under any file name with any extension) that describe the model: its equations, variables, parameters, etc. The model files do not describe what tasks to do with the model. To run the tasks you want to perform with the model, you need first to load the model file into Matlab using the Model.fromFile function. This function creates a model object. Then you write your own m-files using Matlab and Iris functions to perform the desired tasks with the model object.

When writing model files, you can also use the Iris preparsing commands that introduce tools for writing reusable and well-structured model code base and minimize repetitive model code writing tasks.

You can get the model source files syntax highlighted in the Matlab editor to improve the readability of the files, and helps navigate the model more quickly; see the setup instructions.

Guidelines

Topic	Description
Writing source code	Guideline for writing and structuring model source files
Declaring model names	Declare model names: Variables, shocks, parameters
Writing model equations	Write model equations

Categorical list of keywords

Declaring model names: Variables, parameters and shocks

Keyword	Description
!transition-variables	Declare names of transition variables
!transition-shocks	Declare names of transition shocks
!measurement-variables	Declare names fo measurement variables
!measurement-shocks	Declare names of measurement shocks
!parameters	Declare names of parameters
!exogenous-variables	Declare names exogenous variables

Writing model equations

Keyword	Description
!transition-equations	Block of transition equations
!measurement-equations	Block of measurement equations
!dtrends	Block of deterministic trend equations
!links	Define dynamic links
!preprocessor	Preprocessing equations
!postprocessor	Postprocessing equations

Controlling log status of variables

Keyword	Description
!log-variables	List of log-linearised variables
!all-but	Inverse list of log-linearised variables

Defining autoswap pairs

Keyword	Description
!autoswaps-simulate	Definitions of variable-shock pairs to be autoswapped in dynamic simulations
!autoswaps-steady	Definitions of variable-parameter pairs to be autoexogenized in steady-state calculations

Other keywords and syntax

Keyword	Description
min	Define loss function for optimal policy
!!	Steady-state versions of equations
||	Separate alias from the rest of name or equation description
{...}	Lag or lead
&	Reference to the steady-state level of a variable
!ttrend	Linear time trend in deterministic trend equations

Pseudofunctions

Note that pseudofunctions do not start with an exclamation point

Keyword	Description
diff	First difference pseudofunction
roc	Gross rate of change pseudofunction
pct	Percent change
difflog	First log-difference pseudofunction
movavg	Moving average pseudofunction
movgeom	Moving geometric average pseudofunction
movprod	Moving product pseudofunction
movsum	Moving sum pseudofunction

Preparsing keywords

Keyword	Description
%	Line comments
%{ ... %}	Block comments
<...>
!export	Create exportable file to be saved in working directory.
!for	For-loop control structure for automated creation of model source code
!function	Create exportable m-file function to be saved in working directory
!if	Choose block of code based on logical condition.
!import	Include the content of another model file.
!substitutions	Define text substitutions
!switch	Switch among several cases based on expression.