The number of y axis ticks to show.
The position of the ticks will be calculated precisely, so the values on the ticks will not be rounded nicely.
In the case, axis.y.tick.format or axis.y.tick.values will be helpful.
Setting for culling ticks.
If true is set, the ticks will be culled, then only limitted tick text will be shown.
This option does not hide the tick lines. If false is set, all of ticks will be shown.