Highchart - Boxplot - Extra category shown with no data - highcharts

Question

When I'm drawing BOX Plot chart with Highchart like this : JSFiddle
chart: {
type: 'boxplot',
}
where category 2 "Merchant 2" is shown on x-axis even though we don't have data for it.
How can we avoid rendering categories on x-axis when they don't have data in box plot ?
Thank you

Answer 1

There's no built in mechanism in Highcharts that'll filter out and hide "unused" categories.
Workaround:
breaks functionality allows to hide regions on axes. Here's an algorithm that finds the categories that don't have any points above them and applies breaks:
render: function() {
if (redrawEnabled) {
redrawEnabled = false;
var emptyCategories = [],
series = this.series,
xAxis = this.xAxis[0],
categories = xAxis.categories.slice(),
categoryFlags = new Array(categories.length).fill(false), // indicates if any point has a value for category with the given index
breaks = [],
correspondingPoint;
// find out which categories are 'used'
for (var i = 0; i < categories.length; i++) {
for (var ii = 0; ii < series.length; ii++) {
if (!series[ii].visible) {
continue;
}
correspondingPoint = series[ii].data.find((point) => point.x === i);
if (correspondingPoint) {
categoryFlags[i] = true;
break;
}
}
}
// create and apply breaks
categoryFlags.forEach(function(flag, index) {
if (!flag) {
breaks.push({
from: index - 0.5,
to: index + 0.5
});
}
});
//console.log(breaks)
xAxis.update({
breaks: breaks
});
}
redrawEnabled = true;
}
Live demo: http://jsfiddle.net/BlackLabel/fubwdm4x/
The key to understand how this solution works is that the categories are basically just information how to format axis' labels and position ticks. The tickInterval is always 1 and ticks are moved -0.5 to the left. So if you have categories like this: ['Category 1', 'Category 2', 'Category 3'] the positions of ticks are: -0.5, 0.5, 1.5 and 2.5.
API reference: https://api.highcharts.com/highcharts/yAxis.breaks