Help System (web edition) Help System (web edition)LAG=<X step>,<Y step> (in PLOT operation for time series and scatter diagrams) is a specification indicating (in units of the current X and Y scales) the amount of dislocation of the graph in the current coordinate system. <Y step> is optional and default is LAG=0,0. The main purpose of LAG is to enable plotting of lagged variables or positioning of the observation points in the middle of time inter- vals (LAG=0.5).