Syntax: set trange [tmin:tmax]
The range of the parametric variable t is useful in three contexts.
1) In parametric mode plot commands it limits the range of sampling
for both generating functions. See `set parametric`, `set samples`.
2) In polar mode plot commands it limits or defines the range of the
angular parameter theta. See `polar`.
3) In plot or splot commands using 1-dimensional sampled data via
the pseudofile "+". See `sampling 1D`, `special-filenames`.