The set yrange command sets the vertical range that will be displayed. This command turns y axis autoscaling off.
This range may also be specified on the plot command line.
Syntax:
set yrange [{<ymin> : <ymax>}]
where <ymin> and <ymax> terms are constants or expressions.
Both the <ymin> and <ymax> terms are optional. Anything omitted will not be changed, so
set yrange [:10]changes ymax to 10 without affecting ymin.