Annotating a doughnut chart

[rowanwins]

Hi there,

I'm attempting to add an annotation on each segment of a doughnut chart similar to something below

I have an approach which is somewhat working

const plugins = [{
    id: 'centerAnnotations',
    beforeDraw: (chart) => {
      const meta = chart.getDatasetMeta(0);
      const annotations = {};
      meta.data.forEach((element, index) => {
        const angle = (element.startAngle + element.endAngle) / 2;
        const radius = (element.innerRadius + element.outerRadius) / 2;
        
        // Calculate the adjustment needed from center
        const xAdjust = Math.cos(angle) * radius;
        const yAdjust = Math.sin(angle) * radius;

        annotations[`label${index}`] = {
           type: 'label',
           xValue: 'Something',
           xAdjust: xAdjust,
           yAdjust: yAdjust,
           backgroundColor: 'black',
           borderRadius: 12,
           content: meta._parsed[index],
           color: 'white'
        };
      });
      
      // Update the annotations configuration
      chart.options.plugins.annotation.annotations = annotations;
      chart.update()
    }
  }]

This works to produce the above however I am getting a notice in my console
No scale found with id 'x' for annotation 'label0'

I'm guessing that's because a Doughnut chart doesn't have a scale?

Overall the approach is feeling a little clunky for how to position my label relying on the xValue and XAdjust etc, so just wondering if there are any better ways to tackle this.

Thanks,
Rowan

[stockiNail]

@rowanwins that's correct.

From documentation (readme and doc):

Annotations work with line, bar, scatter and bubble charts that use linear, logarithmic, time, or category scales. Furthermore you can use a doughnut label annotation which can be used to add contents (text, image, canvas) in the middle area of the doughnut charts.

Doughnut and pie don't have scale and therefore is not working.

Having a look to your picture, I think you could need the datalabels plugin.

[rowanwins]

Thanks for the advice @stockiNail - much appreciated.