Text tween

Verticale Bar Chart with text tween transition

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

body {
  font: 10px sans-serif;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.x.axis {
  display: none;
}

</style>
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<script>

var margin = {top: 20, right: 30, bottom: 20, left: 30},
    width = 500 - margin.left - margin.right,
    height = 700 - margin.top - margin.bottom;

var formatPercent = d3.format(".3s");

var x = d3.scale.linear()
    .range([0, width]);

var y = d3.scale.ordinal()
    .rangeRoundBands([height, 0], .3, .3);

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom")
    .tickFormat(formatPercent);

var yAxis = d3.svg.axis()
    .scale(y)
    .tickSize(0)
    .orient("left");

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 + ")");

d3.csv("data.csv", function(error, data) {
  
  data.forEach(function(d) {
    d.frequency = +d.frequency;
  });

x.domain([0, d3.max(data, function(d) { return d.frequency; })]);
  y.domain(data.map(function(d) { return d.letter; }));

var bar = svg.selectAll(".bar")
      .data(data)
    .enter().append("g")
      .attr("class", "bar");

bar.append("rect")
      .attr("y", function(d) { return y(d.letter); })
      .attr("height", y.rangeBand())
      .attr("width", 0)
      .style("fill","#1a9850");

bar.append("text")
      .attr("x", 5)
      .attr("y", function(d) { return y(d.letter) + y.rangeBand()/2 + 3; })
      .text(0);

bar.selectAll("rect").transition().ease("quad-out").duration(2000).delay(0).attr("width", function(d) { return x(d.frequency); });
  
  bar.selectAll("text").transition().ease("quad-out").duration(2000).delay(0)
    .attr("x", function(d) { return x(d.frequency) + 3; })
    .tween("text", function(d) {
      var i = d3.interpolate(0, d.frequency);
      return function(t) {
        d3.select(this).text(formatPercent(i(t)));
      };
    });

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

svg.append("g")
      .attr("class", "y axis")
      .call(yAxis)
    .selectAll("text")
      .style("font-weight","bold");

d3.select(self.frameElement).style("height", (height + margin.top + margin.bottom) + "px");

});

</script>

https://d3js.org/d3.v3.min.js