How to make grouped stacked bar chart in d3js?

Question

I've the following d3 chart which is both grouped and each grouped contains a stacked bar. But somehow, I feel this is not a proper way to implement and little complicated. If there was only stacked bar chart, I would have used d3.stack(). Can someone let me know is there any better way to do this?

Snippet as follows:

var data = [
  {
    Category: "cat1",
    type1: 300,
    type2: 450,
    type3: 120
  },
  {
    Category: "cat2",
    type1: 400,
    type2: 100,
    type3: 200
  },
  {
    Category: "cat3",
    type1: 400,
    type2: 100,
    type3: 200
  },
  {
    Category: "cat4",
    type1: 400,
    type2: 100,
    type3: 200
  }
];

var margin = { top: 20, right: 20, bottom: 30, left: 40 },
  width = 500 - margin.left - margin.right,
  height = 500 - margin.top - margin.bottom;
var barWidth = 40;
var x0 = d3.scaleBand().range([0, width]);

var x1 = d3.scaleBand();

var y = d3.scaleLinear().range([height, 0]);

var xAxis = d3.axisBottom(x0);

var yAxis = d3.axisLeft(y).tickFormat(d3.format(".2s"));

var color = d3.scaleOrdinal().range(["#98abc5", "#8a89a6", "#7b6888"]);

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 yBegin;

var innerColumns = {
  column1: ["type1", "type2"],
  column2: ["type3"]
};
var columnHeaders = d3.keys(data[0]).filter(function(key) {
  return key !== "Category";
});
color.domain(
  d3.keys(data[0]).filter(function(key) {
    return key !== "Category";
  })
);
var groupData = data.forEach(function(d) {
  var yColumn = new Array();
  d.columnDetails = columnHeaders.map(function(name) {
    for (ic in innerColumns) {
      if (innerColumns[ic].indexOf(name) >= 0) {
        if (!yColumn[ic]) {
          yColumn[ic] = 0;
        }
        yBegin = yColumn[ic];
        yColumn[ic] += +d[name];
        return {
          name: name,
          column: ic,
          yBegin: yBegin,
          yEnd: +d[name] + yBegin
        };
      }
    }
  });
  d.total = d3.max(d.columnDetails, function(d) {
    return d.yEnd;
  });
});

//console.log(data);
x0.domain(
  data.map(function(d) {
    return d.Category;
  })
);
x1.domain(d3.keys(innerColumns)).range([0, x0.bandwidth()]);

y.domain([
  0,
  1.15 *
    d3.max(data, function(d) {
      return d.total;
    })
]);

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

svg
  .append("g")
  .attr("class", "y axis")
  .call(yAxis);

var stackedbar = svg
  .selectAll(".stackedbar")
  .data(data)
  .enter()
  .append("g")
  .attr("class", "g")
  .attr("transform", function(d) {
    return "translate(" + x0(d.Category) + ",0)";
  });

stackedbar
  .selectAll("rect")
  .data(function(d) {
    return d.columnDetails;
  })
  .enter()
  .append("rect")
  .attr("width", barWidth)
  .attr("x", function(d) {
    return x1(d.column) + (x1.bandwidth() - barWidth) / 2;
  })
  .attr("y", function(d) {
    return y(d.yEnd);
  })
  .attr("height", function(d) {
    return y(d.yBegin) - y(d.yEnd);
  })
  .style("fill", function(d) {
    return color(d.name);
  });

body {
  font: 10px sans-serif;
}
 
.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}
 
.bar {
  fill: steelblue;
}

 

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.6.0/d3.min.js"></script>

Answer 1

I have tried to achieve grouped stacked bar chart using d3.stack(). Here are 2 important parts of my solution:

var datasets=[d3.stack().keys(['type1','type3'])(data),
              d3.stack().keys(['type2'])(data)];

var num_groups=datasets.length;

Here I am using .keys() method of d3.stack to create datasets for each group. After this we can use the code for creating stacked bar chart like this:

d3.range(num_groups).forEach(function(gnum) {
        svg.selectAll('g.group'+gnum)
            .data(datasets[gnum])
            .enter()
            .append('g')
                .attr('fill',accent)
                .attr('class', 'group'+gnum)
            .selectAll('rect')
            .data(d=>d)
            .enter()
            .append('rect')
                .attr('x',(d,i)=>xscale(xlabels[i])+(xscale.bandwidth()/num_groups)*gnum)
                .attr('y',d=>yscale(d[1]))
                .attr('width',xscale.bandwidth()/num_groups)
                .attr('height',d=>yscale(d[0])-yscale(d[1]));
            });

You can see the complete solution here: https://jsfiddle.net/Abhi9kt/28wzdrfk/4/

Answer 2

You might need to have for ... in loops to build that object in your innerColumns like this:

itemLookup= data[0],
category = d3.keys(itemLookup.category),
items = d3.keys(itemLookup.category[type1[0]]),
columnHeaders = [],
innerColumns = (function(){
  var result = {};
  for(var i = 0, ii = category.length; i<ii; i++){
    var holder = [];
    for(var j = 0, jj = items.length; j<jj; j++){
      columnHeaders.push(items[j]+'-'+category[i]);
      holder.push(items[j]+'-'+category[i]);
      result[category[i]] = holder;
    }
  }
  return result;
})()...

You can refer to this for reference: https://jsfiddle.net/kyroskoh/tmec32z0/