TICKSIZE SMALLX BIGX SMALLY BIGY.

Determine tick intervals for BOX. SMALLX refers to the interval
between small tick marks on the x axis, BIGX refers to the x-axis
interval between large ticks and so forth. If BIG is 0, the axis
routine will supply its own intervals according to the label limits.
If SMALL < 0, the axis will have logarithmic tick spacing and BOX
assumes that the limits are logarithms, e.g. -2 and 2 refers to limits
of 0.01 and 100.

Negative values of SMALL and BIG are interpreted as specifying the
tickspacing in the decade 1:10, and are scaled to fit the decades
actually plotted. For instance, if you say
   LIMITS 0 1 3 4
   TICKSIZE -1 10 -0.1 1 BOX
then the x-axis will have small ticks at 2, 3, ..., 9 and big ticks at
1 and 10, while the y axis will have ticks at 1010, 1020, 1030, ...
and big ticks at 1000, 1100, 1200, ...  . The most usual TICKSIZE is
probably -1 10, and this may be written -1 0 for backwards compatibility.

Occasionally you may want to use the same tickspacing in all decades
of your plot. To do this make BIG negative also:
   LIMITS 1.9 2.1 0 1
   TICKSIZE -0.1 -1 0 0 BOX
this is a good way to make an axis very crowded!