Urange

The set urange and set vrange commands sets the parametric ranges used to compute x, y, and z values when in splot parametric mode. If not in parametric mode (see set parametric) then these ranges are not used. This command does not affect x/y autoscaling or x/y ranges.

This range may also be specified on the splot command line when in parametric mode. See plot for more information

Syntax: 

        set urange [{<umin> : <umax>}]

where <umin> and <umax> terms are constants or expressions.

Both the <umin> and <umax> terms are optional. Anything omitted will not be changed, so 

        set urange [:10]
changes umax to 10 without affecting umin. See also set trange.