% movsum  Moving sum pseudofunction.
%
% Syntax
% =======
%
%     movsum(EXPR)
%     movsum(EXPR,K)
%
% Description
% ============
%
% If the second input argument, `K`, is negative, this function expands to
% the moving sum 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 sum 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
%
%     movsum(Z)
%     movsum(Z,-3)
%     movsum(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))
%

% -IRIS Toolbox.
% -Copyright (c) 2007-2012 Jaromir Benes.
