V = instrument(V,Def)
V = instrument(V,Name,Expr)
V = instrument(V,Name,Vec)
V = instrument(V)
V [ VAR ] - VAR object to which forecast instruments will be added.
Def [ char | cellstr ] - Definition of the new forecast conditioning instrument.
Name [ char ] - Name of the new forecast conditiong instrument.
Expr [ char ] - Expression defining the new forecast conditiong instrument.
Vec [ numeric ] - Vector of coeffients to combine the VAR variables to create the new forecast conditioning instrument.