Ordinal histogram

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
function tooltip(text, chart) {
  return (selection) => {
    function mouseover(d) {
      const path = d3.select(this);
      path.classed('highlighted', true);

const mouse = d3.mouse(chart.node());
      const tool = chart.append('g')
        .attr('id', 'tooltip')
        .attr('transform', `translate(${mouse[0] + 5},${mouse[1] + 10})`);

const textNode = tool.append('text')
        .text(text(d))
        .attr('fill', 'black')
        .node();

tool.append('rect')
        .attr('height', textNode.getBBox().height)
        .attr('width', textNode.getBBox().width)
        .style('fill', 'rgba(255, 255, 255, 0.6)')
        .attr('transform', 'translate(0, -16)');

tool.select('text')
        .remove();

tool.append('text').text(text(d));
    }

function mousemove() {
      const mouse = d3.mouse(chart.node());
      d3.select('#tooltip')
        .attr('transform', `translate(${mouse[0] + 15},${mouse[1] + 20})`);
    }

function mouseout() {
      const path = d3.select(this);
      path.classed('highlighted', false);
      d3.select('#tooltip').remove();
    }

selection.on('mouseover.tooltip', mouseover)
      .on('mousemove.tooltip', mousemove)
      .on('mouseout.tooltip', mouseout);
  };
}
    
    
const protoChart = {
  width: window.innerWidth,
  height: window.innerHeight,
  margin: {
    left: 10,
    right: 10,
    top: 10,
    bottom: 10,
  },
};

function chartFactory(opts, proto = protoChart) {
  const chart = Object.assign({}, proto, opts);

chart.svg = d3.select('body')
    .append('svg')
    .attr('id', chart.id || 'chart')
    .attr('width', chart.width - chart.margin.right)
    .attr('height', chart.height - chart.margin.bottom);

chart.container = chart.svg.append('g')
    .attr('id', 'container')
    .attr('transform', `translate(${chart.margin.left}, ${chart.margin.top})`);

return chart;
}
    
const westerosChart = chartFactory({
  margin: { left: 50, right: 50, top: 50, bottom: 50 },
  padding: { left: 10, right: 10, top: 10, bottom: 10 },
});

westerosChart.init = function initChart(chartType, dataUri, ...args) {
	fetch(dataUri)
  	.then(res => res.json())
    .then(data => this[chartType].call(this, data, ...args));
  
  this.innerHeight = this.height - this.margin.top - this.margin.bottom - this.padding.top - this.padding.bottom;
  this.innerWidth = this.width - this.margin.left - this.margin.right - this.padding.left - this.padding.right;
};

westerosChart.histogram = function(_data) {
  const data = _data.data.map(d =>
    Object.assign(d, { death: (d.death.season * 100) + d.death.episode }))
  .sort((a, b) => a.death - b.death);

const episodesPerSeason = 10;
  const totalSeasons = 6;
  const allEpisodes = d3.range(1, totalSeasons + 1).reduce((episodes, s) =>
    episodes.concat(d3.range(1, episodesPerSeason + 1).map(e => (s * 100) + e)), []);
  console.dir(allEpisodes);
  const x = d3.scaleBand()
    .range([0, this.innerWidth])
    .domain(allEpisodes)
    .paddingOuter(0)
    .paddingInner(0.25);

const histogram = d3.histogram()
    .value(d => d.death)
    .thresholds(x.domain());

const bins = histogram(data);
  const y = d3.scaleLinear()
    .domain([0, d3.max(bins, d => d.length)])
    .range([this.innerHeight - 10, 0]);

const bar = this.container.selectAll('.bar')
    .data(bins)
    .enter()
      .append('rect')
      .attr('x', d => x(d.x0))
      .attr('y', d => y(d.length))
      .attr('fill', 'steelblue')
      .attr('width', () => x.bandwidth())
      .attr('height', d => this.innerHeight - 10 - y(d.length));

const xAxis = this.container.append('g')
    .attr('class', 'axis x')
    .attr('transform', `translate(0, ${this.innerHeight - 10})`)
    .call(d3.axisBottom(x).tickFormat(d => `S${(d - (d % 100)) / 100}E${d % 100}`));

xAxis.selectAll('text')
    .each(function (d, i) {
      const yVal = d3.select(this).attr('y');
      d3.select(this).attr('y', i % 2 ? yVal : (yVal * 2) + 2)
    });

xAxis.selectAll('line')
    .each(function (d, i) {
      const y2 = d3.select(this).attr('y2');
      d3.select(this).attr('y2', i % 2 ? y2 : y2 * 2)
    });

bar.call(tooltip((d) => `${d.x0}: ${d.length} deaths`, this.container));
  
d3.select('body').append('p').text(JSON.stringify(bins.map(d => ({start: d.x0, end: d.x1}))));
};

const dataEndpoint = 'https://gist.githubusercontent.com/aendrew/980c3e4b3d0a1ec4b32f734631c29d44/raw/9d91d30ba36fc7244b6cc2cf028d96ae6056628a/GoT-deaths-by-season.json';

westerosChart.init('histogram', dataEndpoint)

</script>
</body>

https://d3js.org/d3.v4.min.js