Help System (web edition)

SER <new_series>=CUM(<old_series>,L) TO <data> 
computes the cumulative sum(s)
   Y(t)=X(t)        for t=1,2,...,L
   Y(t)=Y(t-L)+X(t) for t=L+1,L+2,...
where Y(t)=<new_series>, X(t)=<old_series>.

  S = More information on SER operations