set xlevs lev1 lev2 ... levN
Allows the user to specify each individual labeled tick mark for the X-axis.
set xlevs will override the tick mark interval specified with the
set xlint command.
set
xaxis to specify labeled tick marks and also invoke
set xlevs, then the tick marks lev1
... levN specified with set xlevs will appear
if they fall within the start and
end range specified in the set xaxis command.