Stacked-to-Grouped Bars

Switch between stacked and grouped layouts using sequenced transitions! Animations preserve object constancy and allow the user to follow the data across views. Animation design by Heer and Robertson. Colors and data generation inspired by Byron and Wattenberg.

<!DOCTYPE html>
<meta charset="utf-8">
<style>

body {
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
  margin: auto;
  position: relative;
  width: 960px;
}

text {
  font: 10px sans-serif;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

form {
  position: absolute;
  right: 10px;
  top: 10px;
}

</style>
<form>
  <label><input type="radio" name="mode" value="grouped"> Grouped</label>
  <label><input type="radio" name="mode" value="stacked" checked> Stacked</label>
</form>
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
<script>

var margin = {top: 40, right: 10, bottom: 20, left: 10},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var x = d3.scale.ordinal()
    .domain(d3.range(m))
    .rangeRoundBands([0, width], .08);

var y = d3.scale.linear()
    .domain([0, yStackMax])
    .range([height, 0]);

var color = d3.scale.linear()
    .domain([0, n - 1])
    .range(["#aad", "#556"]);

var xAxis = d3.svg.axis()
    .scale(x)
    .tickSize(0)
    .tickPadding(6)
    .orient("bottom");

var svg = d3.select("body").append("svg")
    .attr("width", width + margin.left + margin.right)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var layer = svg.selectAll(".layer")
    .data(layers)
  .enter().append("g")
    .attr("class", "layer")
    .style("fill", function(d, i) { return color(i); });

var rect = layer.selectAll("rect")
    .data(function(d) { return d; })
  .enter().append("rect")
    .attr("x", function(d) { return x(d.x); })
    .attr("y", height)
    .attr("width", x.rangeBand())
    .attr("height", 0);

rect.transition()
    .delay(function(d, i) { return i * 10; })
    .attr("y", function(d) { return y(d.y0 + d.y); })
    .attr("height", function(d) { return y(d.y0) - y(d.y0 + d.y); });

svg.append("g")
    .attr("class", "x axis")
    .attr("transform", "translate(0," + height + ")")
    .call(xAxis);

d3.selectAll("input").on("change", change);

var timeout = setTimeout(function() {
  d3.select("input[value=\"grouped\"]").property("checked", true).each(change);
}, 2000);

function change() {
  clearTimeout(timeout);
  if (this.value === "grouped") transitionGrouped();
  else transitionStacked();
}

function transitionGrouped() {
  y.domain([0, yGroupMax]);

rect.transition()
      .duration(500)
      .delay(function(d, i) { return i * 10; })
      .attr("x", function(d, i, j) { return x(d.x) + x.rangeBand() / n * j; })
      .attr("width", x.rangeBand() / n)
    .transition()
      .attr("y", function(d) { return y(d.y); })
      .attr("height", function(d) { return height - y(d.y); });
}

function transitionStacked() {
  y.domain([0, yStackMax]);

rect.transition()
      .duration(500)
      .delay(function(d, i) { return i * 10; })
      .attr("y", function(d) { return y(d.y0 + d.y); })
      .attr("height", function(d) { return y(d.y0) - y(d.y0 + d.y); })
    .transition()
      .attr("x", function(d) { return x(d.x); })
      .attr("width", x.rangeBand());
}

// Inspired by Lee Byron's test data generator.
function bumpLayer(n, o) {

function bump(a) {
    var x = 1 / (.1 + Math.random()),
        y = 2 * Math.random() - .5,
        z = 10 / (.1 + Math.random());
    for (var i = 0; i < n; i++) {
      var w = (i / n - y) * z;
      a[i] += x * Math.exp(-w * w);
    }
  }

var a = [], i;
  for (i = 0; i < n; ++i) a[i] = o + o * Math.random();
  for (i = 0; i < 5; ++i) bump(a);
  return a.map(function(d, i) { return {x: i, y: Math.max(0, d)}; });
}

</script>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js