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Documentation for Layer Cake v10, before Svelte 5 runes. Current docs at layercake.graphics

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Stacked area

Jan. 1
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Stacked area chart using D3's stack function. Because this creates a nested data structure, we use Layer Cake's flatten function to pass a flat list to the flatData prop. See the client-side example for the same chart with Layer Cake's stack helper.

This is the server-side rendered version. ssr and percentRange on <LayerCake> put the scales in percentages, so the chart renders before the browser measures it. The axes are HTML components and the marks sit in a <ScaledSvg> that stretches to fit its box.

  • +page.svelte
  • ./_components/AxisX.percent-range.html.svelte
  • ./_components/AxisY.percent-range.html.svelte
  • ./_components/AreaStacked.svelte
  • ./_data/fruit.csv
<script>
  import { LayerCake, ScaledSvg, Html, flatten } from 'layercake';
  import { stack } from 'd3-shape';

  import { scaleOrdinal } from 'd3-scale';
  import { format } from 'd3-format';
  import { timeParse, timeFormat } from 'd3-time-format';

  import AxisX from './_components/AxisX.percent-range.html.svelte';
  import AxisY from './_components/AxisY.percent-range.html.svelte';
  import AreaStacked from './_components/AreaStacked.svelte';

  // The CSV rows are parsed, and their numbers typed, by @rollup/plugin-dsv. See vite.config.js
  import data from './_data/fruit.csv';

  const xKey = 'month';
  // Each stacked point is a [start, end] pair, so the y accessor is those two indexes
  const yKey = [0, 1];
  const cKey = 'key';

  const seriesNames = Object.keys(data[0]).filter(d => d !== xKey);
  const seriesColors = ['#ff00cc', '#ff7ac7', '#ffb3c0', '#ffe4b8'];

  // Turn the date strings into Date objects, on copies so the imported rows stay as they are
  const parseDate = timeParse('%Y-%m-%d');
  const rows = data.map(d => ({ ...d, [xKey]: parseDate(d[xKey]) }));

  const formatLabelX = timeFormat('%b. %-d');
  const formatLabelY = format('~s');

  // d3's stack turns the wide rows into one series per key, each a list of [start, end] pairs
  const stackedData = stack().keys(seriesNames)(rows);
</script>

<div class="chart-container">
  <LayerCake
    ssr
    percentRange
    padding={{ bottom: 20, left: 17 }}
    x={d => d.data[xKey]}
    y={yKey}
    c={cKey}
    cScale={scaleOrdinal()}
    cDomain={seriesNames}
    cRange={seriesColors}
    flatData={flatten(stackedData)}
    data={stackedData}
  >
    <Html>
      <AxisX format={formatLabelX} tickMarks />
      <AxisY format={formatLabelY} />
    </Html>
    <ScaledSvg>
      <AreaStacked />
    </ScaledSvg>
  </LayerCake>
</div>

<style>
  /* Give the wrapper a width and height. LayerCake fills it. */
  .chart-container {
    width: 100%;
    height: 250px;
  }
</style>