15.64.49.2  BASE       - 
     BASE=n - Selects the base for the plot.
  *  LINEAR  this  is useful for non-decimal units.  The labeled ticks are
     put at locations BASE*ROUND*POWER where:
          POWER = a power of 10 1,10,100
          ROUND = 1.0,1.0,2.5, or 5.0
  *  LOG  scaling  large  ticks  are  put  at  powers  of  the base.  This
     determines where ticks are put.  BASE 2 would put labels at 1, 2,  4,
     8, 16,....  If exponential notation is selected then the base is used
     in the notation.