Help System (web edition)

GAP=<ratio of the gap between the bars and the bar width> 
(in PLOT operation for bar charts) has default value 2/3.

GAP=<gap>,<gap_start>,<gap_end> 
(in PLOT operation for bar charts) gives the proportional values
for gaps between the bars (gap), before the first bar (gap_start), and
after the last bar (gap_end).
The default values are gap=2/3*bar_width, gap_start=gap, gap_end=0.
  P = More information on plotting