trange
Syntax:    set trange [tmin:tmax]
The range of the parametric variable t is useful in three contexts.
-  In parametric mode plot commands it limits the range of sampling
 for both generating functions.  See set parametric, set samples.
-  In polar mode plot commands it limits or defines the acceptable
 range of the angular parameter theta during input.  Data points with theta value outside this range are excluded from the plot even if they would otherwise lie inside the plot boundary. See polar.
-  In plot or splot commands using 1-dimensional sampled data via
 the pseudofile "+".  See sampling 1D, special-filenames.