movprod(Expr)
movprod(Expr,K)
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).
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))