Interactive pie chart with input data selector





This post describes how to build an interactive pie chart with input data selector with d3.js. See other pie examples in the pie chart section of the gallery. Watch out: pie chart is most of the time a very bad way to convey information as explained in this post.


Pie chart section

Steps:

  • Warning: are you sure you want to use a pie chart? Learn why it is not recommended.

  • Visit the button section to learn how to build the input selector that triggers a function.

  • Visit the interactivity section to learn about smooth transition in general.

  • Note: transition could be improved to avoid the current weird shape distortion. The code would be way more complicated though, see here for an example.
<!DOCTYPE html>
<meta charset="utf-8">

<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>

<!-- Color scale -->
<script src="https://d3js.org/d3-scale-chromatic.v1.min.js"></script>

<!-- Add 2 buttons -->
<button onclick="update(data1)">Data 1</button>
<button onclick="update(data2)">Data 2</button>

<!-- Create a div where the graph will take place -->
<div id="my_dataviz"></div>

<script>

// set the dimensions and margins of the graph
var width = 450
    height = 450
    margin = 40

// The radius of the pieplot is half the width or half the height (smallest one). I substract a bit of margin.
var radius = Math.min(width, height) / 2 - margin

// append the svg object to the div called 'my_dataviz'
var svg = d3.select("#my_dataviz")
  .append("svg")
    .attr("width", width)
    .attr("height", height)
  .append("g")
    .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");

// create 2 data_set
var data1 = {a: 9, b: 20, c:30, d:8, e:12}
var data2 = {a: 6, b: 16, c:20, d:14, e:19, f:12}

// set the color scale
var color = d3.scaleOrdinal()
  .domain(["a", "b", "c", "d", "e", "f"])
  .range(d3.schemeDark2);

// A function that create / update the plot for a given variable:
function update(data) {

  // Compute the position of each group on the pie:
  var pie = d3.pie()
    .value(function(d) {return d.value; })
    .sort(function(a, b) { console.log(a) ; return d3.ascending(a.key, b.key);} ) // This make sure that group order remains the same in the pie chart
  var data_ready = pie(d3.entries(data))

  // map to data
  var u = svg.selectAll("path")
    .data(data_ready)

  // Build the pie chart: Basically, each part of the pie is a path that we build using the arc function.
  u
    .enter()
    .append('path')
    .merge(u)
    .transition()
    .duration(1000)
    .attr('d', d3.arc()
      .innerRadius(0)
      .outerRadius(radius)
    )
    .attr('fill', function(d){ return(color(d.data.key)) })
    .attr("stroke", "white")
    .style("stroke-width", "2px")
    .style("opacity", 1)

  // remove the group that is not present anymore
  u
    .exit()
    .remove()

}

// Initialize the plot with the first dataset
update(data1)

</script>

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