Basic stackedarea chart from wide input format




This post describes how to build a very basic stacked area chart with d3.js. Note that input dataset is at the wide (untidy) format: each group is provided in a specific column. See another basic example starting from long (tidy) format here. You can see many other examples in the stacked area chart section of the gallery.


Stacked area section

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.

  • Data is available here. Note the wide (untidy) format: each group is provided in a specific column.

  • To build a stacked area chart, data must be stacked, using the d3.stack() function.

  • Once the new coordinates are available, shapes can be added through path, using the d3.area() helper.
<!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: 20, right: 30, bottom: 30, left: 55},
    width = 460 - 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 + ")");

// Parse the Data
d3.csv("https://raw.githubusercontent.com/holtzy/data_to_viz/master/Example_dataset/5_OneCatSevNumOrdered_wide.csv", function(data) {

  // List of groups = header of the csv files
  var keys = data.columns.slice(1)

  // Add X axis
  var x = d3.scaleLinear()
    .domain(d3.extent(data, function(d) { return d.year; }))
    .range([ 0, width ]);
  svg.append("g")
    .attr("transform", "translate(0," + height + ")")
    .call(d3.axisBottom(x).ticks(5));

  // Add Y axis
  var y = d3.scaleLinear()
    .domain([0, 200000])
    .range([ height, 0 ]);
  svg.append("g")
    .call(d3.axisLeft(y));

  // color palette
  var color = d3.scaleOrdinal()
    .domain(keys)
    .range(['#e41a1c','#377eb8','#4daf4a','#984ea3','#ff7f00','#ffff33','#a65628','#f781bf'])

  //stack the data?
  var stackedData = d3.stack()
    .keys(keys)
    (data)
    //console.log("This is the stack result: ", stackedData)

  // Show the areas
  svg
    .selectAll("mylayers")
    .data(stackedData)
    .enter()
    .append("path")
      .style("fill", function(d) { console.log(d.key) ; return color(d.key); })
      .attr("d", d3.area()
        .x(function(d, i) { return x(d.data.year); })
        .y0(function(d) { return y(d[0]); })
        .y1(function(d) { return y(d[1]); })
    )

})

</script>

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