Slope chart

before and after

Before and after, two points, one line each. Devastatingly clear.

Format.d3
Length81 lines
Includesnone

The source

81 lines of D3 JavaScript, and uses only the bundled D3 build. Copy it, or open the template inside Gnomon and render it as it is.

// Slope chart — two points in time, one line each.
// The whole message is in the direction of the slopes, so colour by
// improvement/regression and let everything else recede.

const rows = [
  { name: 'Quote Engine',      before: 82, after: 91 },
  { name: 'Broker Portal',     before: 74, after: 79 },
  { name: 'Customer Portal',   before: 68, after: 88 },
  { name: 'Contact Centre',    before: 61, after: 44 },
  { name: 'Policy Admin Core', before: 39, after: 42 },
  { name: 'Legacy Ledger',     before: 55, after: 31 },
  { name: 'Underwriting',      before: 77, after: 84 },
  { name: 'Risk Scoring',      before: 88, after: 93 },
  { name: 'Data Lakehouse',    before: 71, after: 86 },
  { name: 'BI & Reporting',    before: 64, after: 63 },
];

const margin = { top: 54, right: 190, bottom: 30, left: 190 };
const y = d3.scaleLinear()
    .domain(d3.extent([...rows.map(d => d.before), ...rows.map(d => d.after)])).nice()
    .range([height - margin.bottom, margin.top]);
const xLeft = margin.left;
const xRight = width - margin.right;

const up = theme.palette[4];
const down = theme.palette[2];
const flat = theme.muted;
const colourOf = d => {
  const delta = d.after - d.before;
  if (delta > 2) return up;
  if (delta < -2) return down;
  return flat;
};

const svg = d3.select(container).append('svg')
    .attr('viewBox', [0, 0, width, height])
    .attr('width', width)
    .attr('height', height)
    .attr('font-family', 'system-ui, sans-serif')
    .attr('font-size', 11);

svg.append('g')
    .attr('stroke-width', 2)
  .selectAll('line')
  .data(rows)
  .join('line')
    .attr('x1', xLeft).attr('y1', d => y(d.before))
    .attr('x2', xRight).attr('y2', d => y(d.after))
    .attr('stroke', colourOf)
    .attr('stroke-opacity', 0.85);

for (const [x, key, anchor, dx] of [[xLeft, 'before', 'end', -10], [xRight, 'after', 'start', 10]]) {
  const g = svg.append('g');
  g.selectAll('circle')
    .data(rows)
    .join('circle')
      .attr('cx', x)
      .attr('cy', d => y(d[key]))
      .attr('r', 4)
      .attr('fill', colourOf);
  g.selectAll('text')
    .data(rows)
    .join('text')
      .attr('x', x + dx)
      .attr('y', d => y(d[key]))
      .attr('dy', '0.35em')
      .attr('text-anchor', anchor)
      .attr('fill', theme.foreground)
      .text(d => `${d.name} ${d[key]}`);
}

svg.append('g')
    .attr('fill', theme.muted)
    .attr('font-weight', 600)
  .selectAll('text')
  .data([['2024 health', xLeft, 'end'], ['2026 health', xRight, 'start']])
  .join('text')
    .attr('x', d => d[1] + (d[2] === 'end' ? -10 : 10))
    .attr('y', margin.top - 24)
    .attr('text-anchor', d => d[2])
    .text(d => d[0]);

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