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Column annotatedEdit

Since we want an ordinal x-axis and Layer Cake defaults to a linear scale, pass in a custom scale to xScale with a few formatting options. Set the y-scale to always start at 0 so you don't show misleading differences between groups. For the annotation arrowhead, note that, depending on your app structure, such as if you're using Sapper, you may need to provide an explicit link to your SVG marker id, such as in ./components/Arrows.svelte using window.location.href.

<script>
  import { LayerCake, Svg, Html } from 'layercake';
  import { scaleBand } from 'd3-scale';

  import Column from './components/Column.svelte';
  import AxisX from './components/AxisX.svelte';
  import AxisY from './components/AxisY.svelte';
  import Annotations from './components/Annotations.svelte';
  import Arrows from './components/Arrows.svelte';
  import ArrowheadDef from './components/ArrowheadDef.svelte';

  // This example loads csv data as json using @rollup/plugin-dsv
  import data from './data/groups.csv';

  const xKey = 'year';
  const yKey = 'value';

  const annotations = [
    {
      text: 'Example text...',
      top: '18%',
      left: '30%',
      arrows: [{
        clockwise: false, // true or false, defaults to true
        source: {
          anchor: 'left-bottom', // can be `{left, middle, right},{top-middle-bottom}`
          dx: -2,
          dy: -7
        },
        target: {
          x: '28%',
          y: '75%'
        }
      },
      {
        source: {
          anchor: 'right-bottom',
          dy: -7,
          dx: 5
        },
        target: {
          x: '68%',
          y: '48%'
        }
      }]
    }
  ];

  data.forEach(d => {
    d[yKey] = +d[yKey];
  });
</script>

<style>
  /*
    The wrapper div needs to have an explicit width and height in CSS.
    It can also be a flexbox child or CSS grid element.
    The point being it needs dimensions since the <LayerCake> element will
    expand to fill it.
  */
  .chart-container {
    width: 100%;
    height: 100%;
  }
</style>

<div class="chart-container">
  <LayerCake
    padding={{ top: 0, right: 0, bottom: 20, left: 20 }}
    x={xKey}
    y={yKey}
    xScale={scaleBand().paddingInner([0.02]).round(true)}
    xDomain={['1979', '1980', '1981', '1982', '1983']}
    yDomain={[0, null]}
    data={data}
  >
    <Svg>
      <Column/>
      <AxisX
        gridlines={false}
      />
      <AxisY
        gridlines={false}
      />
    </Svg>

    <Html>
      <Annotations {annotations}/>
    </Html>

    <Svg>
      <ArrowheadDef/>
      <Arrows {annotations}/>
    </Svg>
  </LayerCake>
</div>