Welcome to d3aday! If this is your first time, we recommend reading the about page before jumping in.

The Inspiration

The inspiration for this exercise was the stacked bar chart showing Democratic primary candidate endorsements on Fivethirtyeight.com

Stacked Bar Chart Inspiration

I like this chart a lot. It’s intuitive, clear, gets the big picture across at a glance, but allows for drilling down into the details as well. Also, floating heads are always hilarious.

The Exercise

Stacked bar charts (and similar things like streamgraphs) can be a bit of a challenge. The D3.js API for stacks took me some time to wrap my head around. But it’s definitely doable.

In addition to the official D3.js documentation on stacks, I found Bostock’s Tidy Stacked Area Chart example helpful as well.

For this exercise, we’ll use some data I generated on high calorie foods. Each food has a breakdown of macronutrients, and the chart should show total calories as well. The data can be found here.

I lifted the color pallette directly from the inspiration chart. Hey, it’s a great pallette.

A Solution

My solution looks like this:

Stacked Bar Chart Solution

Lentil soup - the next avocado?

The code is below, but I encourage you to try your hand at this exercise on your own. Complete code and working example (with tooltip rollovers for the stacks) can be found on codepen.

// Initial setup / set margins by convention
const margin = {top: 0, right: 30, bottom: 20, left: 90},
    width = 500 - margin.left - margin.right,
    height = 700 - margin.top - margin.bottom,
    svg = d3.select(".chart")
        .attr("width", width + margin.left + margin.right)
        .attr("height", height + margin.top + margin.bottom);

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

const URL = "https://gist.githubusercontent.com/fraziern/084ab4f8535083ebf90ada173faae054/raw/19f44640f4f193850a1392305a1824e922214d40/foodcalories.csv";

function createChart(data) {
  var stack = d3.stack()
    .keys(["Carbs", "Fat", "Protein"])

  var series = stack(data);
  const xMax = d3.max(series, y => d3.max(y, d => d[1]));
  var x = d3.scaleLinear()
    .domain([0, xMax])
    .range([0, width]);
  var y = d3.scaleBand()
    .domain(data.map(d => d.Food))
    .range([0, height])
  color = d3.scaleOrdinal()
    .domain(series.map(d => d.key))
    .range(d3.quantize(d3.interpolateHcl("#B4D8E9", "#3CA7DC"), series.length));
      .attr("fill", d => color(d.key))
    .data(d => d)
      .attr("y", (d, i) => y(d.data.Food))
      .attr("x", d => x(d[0]))
      .attr("width", d => x(d[1]) - x(d[0]))
      .attr("height", y.bandwidth())
      .on("mouseout", () => tooltip.style("display", "none"))
      .on("mouseover", displayTooltip);
  // y axis
  yAxis = g => g
  // data labels
      .attr("class", "data-label")
      .text(d => d.Total)
      .attr("y", d => y(d.Food))
      .attr("x", d => x(d.Total))
      .attr("dy", y.bandwidth() / 2)
      .attr("dx", "1em")
      .attr("alignment-baseline", "middle");
  // tooltip
  var tooltip = chart.append("g")
    .attr("class", "tooltip")
    .style("display", "none");

    .attr("x", 15)
    .attr("dy", "-0.2em")
    .style("text-anchor", "middle");
  function displayTooltip(d, i) {
    var thisName = d3.select(this.parentNode).datum().key;
    var thisValue = d.data[thisName];
    var xPosition = x(d[0]);
    var yPosition = y(d.data.Food);
    tooltip.attr("transform", "translate(" + xPosition + "," + yPosition + ")");
    tooltip.select("text").text(thisName + ": " + thisValue)
    tooltip.style("display", null);

  (d, i, columns) => (
    d.Total = d3.sum(columns, c => d[c]),     d))
  .then(d => d.sort((a, b) => b.Total - a.Total))
  .then(d => d.slice(0,10))