Stacked Barchart with Transitions

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.4/lodash.min.js"></script>
  <style>s
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
<script>
  
  var	margin = {top: 20, right: 20, bottom: 30, left: 40},
			outerWidth = 960,
      outerHeight = 500,
      width = outerWidth - margin.left - margin.right,
      height = outerHeight - margin.top - margin.bottom,
      svg = d3.select("body").append("svg")
        .attr("width", outerWidth)
        .attr("height", outerHeight),
      g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")"),
      data = undefined,
      serie,
      serieEnter,
      rect,
      rectEnter;

var x = d3.scaleBand()
  .rangeRound([0, width])
  .padding(0.1)
  .align(0.1);

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

var z = d3.scaleOrdinal()
      .range(["#98abc5", "#8a89a6", "#7b6888", "#6b486b", "#a05d56", "#d0743c", "#ff8c00"]);

var stack = d3.stack();

d3.csv("data.csv", type, function(error, iData) {
    if (error) throw error;

data = iData;
    data.sort(function(a, b) { return b.total - a.total; });

x.domain(data.map(function(d) { return d.State; }));
    y.domain([0, d3.max(data, function(d) { return d.total; })]).nice();
    z.domain(data.columns.slice(1));
		
    // Button to generate new data.
    g.append("rect")
    	.attr("class", "btn-update-data")
    	.attr("width", 60)
      .attr("height", 20)
      .attr("transform", "translate("+ (width-200) +", 0)")
      .attr("fill", "red")
    	.on("click", function() {
				updateChart(jumbleData(data), false);
      });
    
    var legend = g.selectAll(".legend")
      .data(data.columns.slice(1).reverse())
      .enter().append("g")
        .attr("class", "legend")
        .attr("transform", function(d, i) { return "translate(0," + i * 20 + ")"; })
        .style("font", "10px sans-serif");

legend.append("rect")
        .attr("x", width - 18)
        .attr("width", 18)
        .attr("height", 18)
        .attr("fill", z);

legend.append("text")
        .attr("x", width - 24)
        .attr("y", 9)
        .attr("dy", ".35em")
        .attr("text-anchor", "end")
        .text(function(d) { return d; });
    
    updateChart(data, true);

});
  
  // Update the chart with the specified data.
  function updateChart(iData, initializing) {
    console.log("************* ENTER-updateChart")
    console.log("iData", iData)
    
    // ----------------------------------------------------------------
    // SERIE
    // ----------------------------------------------------------------
    
    // SERIE ENTER -----------------------
    var stacks = stack.keys(iData.columns.slice(1))(iData);
    // flatten stacks array
    var stackData = [];
    for (var i = 0; i < stacks.length; i++) {
      for (var j = 0; j < stacks[i].length; j++) {
        stacks[i][j].key = stacks[i].key;
        var factor = Math.random() + 0.5;
        factor = factor <= 1 ? factor : factor - 1;
        var diff = Math.round(stacks[i][j][0] * factor);
        stacks[i][j][0] = stacks[i][j][0] - diff;
        
        stackData.push(stacks[i][j]);
      }
    }
    if (initializing) {
      // Parent bar
      serieEnter = g.append("g").attr("class", "rects");
      
      rect = serieEnter.selectAll("rect.chart-rect")
              .data(stackData)
              .enter()
              .append("rect")
              .attr("class", "chart-rect")
              .attr("state", function(d) {return d.data.State; })
              .attr("x", function(d) { return x(d.data.State); })
              .attr("y", function(d) { return y(d[1]); })
              .attr("height", function(d) { return y(d[0]) - y(d[1]); })
              .attr("width", x.bandwidth())
              .attr("fill", function(d) {  return z(d.key)});
    } else {
      serieEnter = g.select("g.rects");
      rect = serieEnter.selectAll("rect.chart-rect")
              .data(stackData);
      
      rect.transition()
              .attr("state", function(d) {return d.data.State; })
              .attr("y", function(d) { return y(d[1]); })
              .attr("height", function(d) { return y(d[0]) - y(d[1]); })
              .duration(1000);
    }

// ----------------------------------------------------------------
    // AXES
    // ----------------------------------------------------------------
    
    if (initializing) {
      // X axis
      g.append("g")
          .attr("class", "axis axis-x")
          .attr("transform", "translate(0," + height + ")")
          .call(d3.axisBottom(x));
  
      // Y axis
      g.append("g")
          .attr("class", "axis axis-y")
          .call(d3.axisLeft(y).ticks(10, "s"))
        .append("text")
          .attr("x", 2)
          .attr("y", y(y.ticks(10).pop()))
          .attr("dy", "0.35em")
          .attr("text-anchor", "start")
          .attr("fill", "#000")
          .text("Population");
    } else {
      // remove xAxis
      g.select("g.axis-x").remove();
      
      // X axis
      g.append("g")
          .attr("class", "axis axis-x")
          .attr("transform", "translate(0," + height + ")")
          .call(d3.axisBottom(x));
    }
  }
  
  // Jumble the data so we can test transitioning to new data.
  function jumbleData(iData) {
		
//     console.log("*************** ENTER-jumbleData")
//     console.log("iData", iData)
    
    var result = undefined;
    var oldColumns = iData.columns;
    var data = _.cloneDeep(iData);		// for some reason, clone() removes the 'columns' obj in iData, so we don't need to remove it after cloning... nice
    
//     console.log("data", data)
        
    for (var i = 0; i < data.length; i++) {

//       console.log("------------- i", i)
      
      var cur = data[i];      
      var itemToSwapDataWith = _.sample(data)
      
//       console.log("cur", cur)
//       console.log("itemToSwapDataWith", itemToSwapDataWith)
      
      // Swap state names for the 2 objects, so their data is swaped, essentially.
      var curState = cur.State;
      cur.State = itemToSwapDataWith.State;
      itemToSwapDataWith.State = curState;

//       console.log("----- SWAP -----")
//       console.log("cur", cur)
//       console.log("itemToSwapDataWith", itemToSwapDataWith)

}
    
    data.columns = oldColumns;
    result = data;
    
//     console.log("result", result)
    
    return result;
    
  }

function type(d, i, columns) {
    for (i = 1, t = 0; i < columns.length; ++i) t += d[columns[i]] = +d[columns[i]];
    d.total = t;
    return d;
  }
  
</script>
</body>

https://d3js.org/d3.v4.min.js

https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.16.4/lodash.min.js