Category Axis

Specifying any of the settings above defines the x-axis as type: 'category' if not defined otherwise. For more fine-grained control of category labels, it is also possible to add labels as part of the category axis definition. Doing so does not apply the global defaults.

Globally:

Namespace: options.scales[scaleId]

Namespace: options.scales[scaleId].ticks

Internally category scale uses label indices