movprod

Moving product pseudofunction

Syntax

movprod(Expr)
movprod(Expr,K)

Description

If the second input argument, K, is negative, this function expands to the moving product of the last K periods (including the current period), i.e.

((Expr)*(Expr{-1})* ... *(Expr{-(K-1)})

where Expr{-N} derives from Expr and has all its time subscripts shifted by -N (if specified).

If the second input argument, K, is positive, this function expands to the moving product of the next K periods ahead (including the current period), i.e.

((Expr)*(Expr{1})* ... *(Expr{K-1})

If the second input argument, K, is not specified, the default value -4 is used (based on the fact that most of the macroeconomic models are quarterly).

Example

The following three lines

movprod(Z)
movprod(Z,-3)
movprod(X+Y{-1},2)

will expand to

((Z)*(Z{-1})*(Z{-2})*(Z{-3}))
((Z)*(Z{-1})*(Z{-2}))
((X+Y{-1})*(X{1}+Y))