Sets or returns the number of categories to show between axis tick marks.
This property corresponds to the "Interval between tick marks" property under "Axis Options".
By default, this value is automatic. It will return 1 in this case. At this time, there is no way to distinguish between when this property is automatic, and when this property is set to 1. Nor is there a way to set this property back to automatic.
The minimum allowed value is 1. The maximum allowed value is 31999. If you set this property to a value out of bounds, it will be clamped to the nearest allowed value.
This property has no effect when the category axis will be interpreted as a date axis.