[D3] Build a Column Chart with D3 v4

Column and bar charts are staples of every visualization library. They also make a great project for combining the essential pieces of D3 like selections, scales, axes, and SVG elements. This lesson walks you through the process of creating an essential chart type with all the required components.

The dataset looks like:

var data = [
  {score: 63, subject: 'Mathematics'},
  {score: 82, subject: 'Geography'},
  {score: 74, subject: 'Spelling'},
  {score: 97, subject: 'Reading'},
  {score: 52, subject: 'Science'},
  {score: 74, subject: 'Chemistry'},
  {score: 97, subject: 'Physics'},
  {score: 52, subject: 'ASL'}
];

We want 'score' map to 'Y' axis and 'subject' map to 'X' axis.

For 'Y' axis is pretty, we can use 'scaleLinear'.

For 'X' axis we can use 'scaleBand'.

var data = [
  {score: 63, subject: 'Mathematics'},
  {score: 82, subject: 'Geography'},
  {score: 74, subject: 'Spelling'},
  {score: 97, subject: 'Reading'},
  {score: 52, subject: 'Science'},
  {score: 74, subject: 'Chemistry'},
  {score: 97, subject: 'Physics'},
  {score: 52, subject: 'ASL'}
];

var margin = { top: 10, right: 20, bottom: 65, left: 30 };
var width = 400 - margin.left - margin.right;
var height = 600 - margin.top - margin.bottom;

var svg = d3.select('.chart')
  .append('svg')
    .attr('width', width + margin.left + margin.right)
    .attr('height', height + margin.top + margin.bottom)
    .call(responsivefy)
  .append('g')
    .attr('transform', 'translate(' + margin.left + ', ' + margin.top + ')');

/**
 * Add Y axis
 */
var yScale = d3.scaleLinear()
  .domain([0, 100])
  .range([height, 0]);
var yAxis = d3.axisLeft(yScale);
svg.call(yAxis);

/**
 * Add X axis
 */
var xScale = d3.scaleBand()
  .padding(0.2)
  .domain(data.map(d => d.subject))
  .range([0, width]); 

var xAxis = d3.axisBottom(xScale)
  .ticks(5)
  .tickSize(10)
  .tickPadding(5);
svg
  .append('g')
    .attr('transform', `translate(0, ${height})`)
  .call(xAxis)
  .selectAll('text')
  .attr('text-anchor', 'end')
  .attr('transform', 'rotate(-45)'); // Rotate the text so texts won't conflict

/**
 * Draw the columns
 */
svg.selectAll('rect')
    .data(data)
    .enter()
    .append('rect')
    .attr('x', d => xScale(d.subject))
    .attr('y', d => yScale(d.score))
    .attr('width', d => xScale.bandwidth())
    .attr('height', d => height-yScale(d.score)); 

function responsivefy(svg) {
  // get container + svg aspect ratio
  var container = d3.select(svg.node().parentNode),
      width = parseInt(svg.style("width")),
      height = parseInt(svg.style("height")),
      aspect = width / height;

  // add viewBox and preserveAspectRatio properties,
  // and call resize so that svg resizes on inital page load
  svg.attr("viewBox", "0 0 " + width + " " + height)
      .attr("preserveAspectRatio", "xMinYMid")
      .call(resize);

  // to register multiple listeners for same event type,
  // you need to add namespace, i.e., 'click.foo'
  // necessary if you call invoke this function for multiple svgs
  // api docs: https://github.com/mbostock/d3/wiki/Selections#on
  d3.select(window).on("resize." + container.attr("id"), resize);

  // get width of container and resize svg to fit it
  function resize() {
      var targetWidth = parseInt(container.style("width"));
      svg.attr("width", targetWidth);
      svg.attr("height", Math.round(targetWidth / aspect));
  }
}