jQuery PolarChart - argumentAxis.tick
Ticks divide an axis into equal sections by a step whose value is determined automatically, or by the tickInterval and axisDivisionFactor properties of an axis. Ticks improve the readability of charts, but are not visible in the PolarChart UI component by default. To set up tick configuration properties, define the tick object within the argumentAxis or valueAxis configuration object. To set common properties for all ticks in a chart, define the tick object within the commonAxisSettings configuration object. Note that the values that are set for an individual axis override the corresponding common values.
Main article: shift for ticks in the Chart