Basic boxplot in d3.js

Steps:

The Html part of the code just creates a div that will be modified by d3 later on.

The first part of the javascript code set a svg area. It specify the chart size and its margin. Read more.

In this example dummy data are created. It's a vector format. See here to work from a .csv

Note that quantiles, median, min and max are computed one by one. See data-to-viz to understand what these values are.

The Y scale can now be added. Read here if you're not used to it.

Finally, the box can be added, it is just one rect, and 2 lines elements.

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

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

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

<script>

// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 40},
  width = 400 - margin.left - margin.right,
  height = 400 - margin.top - margin.bottom;

// append the svg object to the body of the page
var svg = d3.select("#my_dataviz")
.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 + ")");

// create dummy data
var data = [12,19,11,13,12,22,13,4,15,16,18,19,20,12,11,9]

// Compute summary statistics used for the box:
var data_sorted = data.sort(d3.ascending)
var q1 = d3.quantile(data_sorted, .25)
var median = d3.quantile(data_sorted, .5)
var q3 = d3.quantile(data_sorted, .75)
var interQuantileRange = q3 - q1
var min = q1 - 1.5 * interQuantileRange
var max = q1 + 1.5 * interQuantileRange

// Show the Y scale
var y = d3.scaleLinear()
  .domain([0,24])
  .range([height, 0]);
svg.call(d3.axisLeft(y))

// a few features for the box
var center = 200
var width = 100

// Show the main vertical line
svg
.append("line")
  .attr("x1", center)
  .attr("x2", center)
  .attr("y1", y(min) )
  .attr("y2", y(max) )
  .attr("stroke", "black")

// Show the box
svg
.append("rect")
  .attr("x", center - width/2)
  .attr("y", y(q3) )
  .attr("height", (y(q1)-y(q3)) )
  .attr("width", width )
  .attr("stroke", "black")
  .style("fill", "#69b3a2")

// show median, min and max horizontal lines
svg
.selectAll("toto")
.data([min, median, max])
.enter()
.append("line")
  .attr("x1", center-width/2)
  .attr("x2", center+width/2)
  .attr("y1", function(d){ return(y(d))} )
  .attr("y2", function(d){ return(y(d))} )
  .attr("stroke", "black")
</script>

Most basic boxplot in d3.js

Steps:

Related blocks →