Basic stacked barplot 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.

The d3.stack() function is used to stack the data: it computes the new position of each group on the Y axis

The output of d3.stack() can be used to create a set of rect as for a normal barplot.

<!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: 20, left: 50},
    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/D3-graph-gallery/master/DATA/data_stacked.csv", function(data) {

  // List of groups = what we want on the X axis
  var keys = d3.map(data, function(d){return(d.group)}).keys()
  var subgroups = d3.map(data, function(d){return(d.subgroup)}).keys()

  // Add X axis
  var x = d3.scaleBand()
      .domain(keys)       // This is what is written on the Axis: from 0 to 100
      .range([0, width])                       // This is where the axis is placed: from 100 px to 800px
      .padding([0.2])
  svg.append("g")
    .attr("transform", "translate(0," + height + ")")
    .call(d3.axisBottom(x).tickSizeOuter(0));

  // Add Y axis
  var y = d3.scaleLinear()
    .domain([0, 200])
    .range([ height, 0 ]);
  svg.append("g")
    .call(d3.axisLeft(y));

  // color palette
  var color = d3.scaleOrdinal()
    .domain(subgroups)
    .range(['#e41a1c','#377eb8','#4daf4a'])

  // Need to nest = group the data first.
  var nestedData = d3.nest()
    .key(function(d) { return d.group; })
    .rollup(function(d) { console.log(d) ; return d.subgroup; })
    .entries(data)
  console.log(nestedData)

  // And then to stack the data by subgroups
  var stackedData = d3.stack()
    .keys(subgroups)
    .value(function(d, key){
      console.log(d.values.values)
      return(1)
    })(nestedData)
  console.log(stackedData)
})

</script>

Most basic stacked barplot in d3.js

Steps:

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