!switch

Switch among several cases based on expression.

Syntax with an otherwise clause

!switch Expr
    !case Balue1
        Block1
    !case Balue2
        Block2
    ...
    !otherwise
        OtherwiseBlock
!end

Syntax without an otherwise clause

!switch Expr
    !case Value1
        Block1
    !case Value2
        Block2
    ...
!end

Description

The !switch...!case...!otherwise...!end command works the same way as its counterpart in the Matlab programming language.

Use the !switch...!case...!end command to create a larger number of branches of the model code. Which block of code is actually read in and which blocks are discarded depends on which value in the !case clauses matches the value of the !switch expression. This works exactly as the switch...case...end command in Matlab. The expression after the !switch part of the command must must be a valid Matlab expression, and can refer to the model parameters, or to other fields included in the parameter database passed in when you run the model function; see the option 'assign='.

If the expression fails to be matched by any value in the !case clauses, the branch in the !otherwise clause is used. If it is a !switch command without the !otherwise clause, the whole command is discarded. The Matlab function isequal is used to match the !switch expression with the !case values.

Example

!switch policy_regime

    !case 'IT'
        r = rho*r{-1} + (1-rho)*kappa*pie{4} + epsilon;

    !case 'Managed_exchange_rate'
        s = s{-1} + epsilon;

    !case 'Constant_money_growth'
        m-m{-1} = m{-1}-m{-2} + epsilon;

!end

When reading the model file in, create a parameter database, include at least a field named policy_regime in it, and use the option 'assign=' to pass the database in. Note that you do not need to declare policy_regime as a parameter in the model file.

P = struct( );
P.policy_regime = 'Managed_exchange_rate';
...
m = model('my.model','assign',P);

In this case, the managed exchange rate policy rule, s = s{-1} + epsilon; is read in and the rest of the !switch command is discarded. To use another branch of the !switch command you need to re-read the model file again with a different value assigned to the policy_regime field of the input database.