Decimal tickIntervals should be disallowed for a category axis.

[jgerigmeyer]

If using a category axis without setting allowDecimals: false, normalizeTickInterval can sometimes return a tickInterval of 2.5. This causes a tick.pos of 2.5, which in turn causes categories[pos] to be undefined and results in an incorrect label.

I would think this could be solved in a number of ways:

1. Not calling normalizeTickInterval on a category axis, by adding && !categories to https://github.com/highslide-software/highcharts.com/blob/master/js/highcharts.4.1.4.js#L7412.
2. Adding !!categories to the fourth arg passed to normalizeTickInterval: https://github.com/highslide-software/highcharts.com/blob/master/js/highcharts.4.1.4.js#L7420.
3. Defaulting allowDecimals to false for a category axis.

[TorsteinHonsi]

Can you show a live demo of this? You can use http://jsfiddle.net/highcharts/as25s8ga/ as a starting point.

[jgerigmeyer]

Sure. You can see a live demo of the bug at http://jsfiddle.net/jgerigmeyer/h705n915/.

I'm not sure if it only happens when you have two linked category axes, but that seemed to be the easiest way to demonstrate it.

[jgerigmeyer]

👍