If a data file is plotted without the width being specified in the fifth column, or a function is plotted, the width of each box is set by the set boxwidth command. If a width is given after the set boxwidth command then this is used as the width. Otherwise the width of each box will be calculated automatically so that it touches the adjacent boxes.
Syntax:
set boxwidth {<width>}
show boxwidth
To set the box width to automatic use the command
set boxwidth