如何在栏上设置自定义标签？

如下面的快照所示，如何在图表上设置Yes和No标签？

D3代码：

var data = [
    {
        "episode": "Ep. 01",
        "yes": "60",
        "no": "40"
    },
    {
        "episode": "Ep. 02",
        "yes": "70",
        "no": "30"
    },
    {
        "episode": "Ep. 03",
        "yes": "50",
        "no": "50"
    },
    {
        "episode": "Ep. 04",
        "yes": "90",
        "no": "10"
    },
    {
        "episode": "Ep. 05",
        "yes": "30",
        "no": "70"
    },
    {
        "episode": "Ep. 06",
        "yes": "60",
        "no": "40"
    },
    {
        "episode": "Ep. 07",
        "yes": "70",
        "no": "30"
    },
    {
        "episode": "Ep. 08",
        "yes": "50",
        "no": "50"
    },
    {
        "episode": "Ep. 09",
        "yes": "90",
        "no": "10"
    },
    {
        "episode": "Ep. 10",
        "yes": "30",
        "no": "70"
    }
];

var margin = {top: 20, right: 100, bottom: 30, left: 40},
    width = 600 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var x = d3.scale.ordinal()
.rangeRoundBands([0, width], .1);

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

var color = d3.scale.ordinal()
.range(["#B4D92A", "#FF3332"]);

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

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

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) {
color.domain(d3.keys(data[0]).filter(function(key) { return key !== "episode"; }));

data.forEach(function(d) {
    var y0 = 0;
    d.ages = color.domain().map(function(name) { return {name: name, y0: y0, y1: y0 += +d[name]}; });
    d.ages.forEach(function(d) { d.y0 /= y0; d.y1 /= y0; });
});

//data.sort(function(a, b) { return b.ages[0].y1 - a.ages[0].y1; });

x.domain(data.map(function(d) { return d.episode; }));

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

svg.selectAll(".ellipse")
.data(data)
.enter()
.append("ellipse")
.attr("cx", function(d) { return x(d.episode) + 14; })
.attr("cy", function(d) { return y(0); })
.attr("rx", 18)
.attr("ry", 5)
.style("fill", "#728220");

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

episode.selectAll("rect")
.data(function(d) { return d.ages; })
.enter().append("rect")
.attr("width", x.rangeBand() - 15)
.attr("y", function(d) { return y(d.y1); })
.attr("height", function(d) { return y(d.y0) - y(d.y1); })
.style("fill", function(d) { return color(d.name); })
/*.attr("rx", 5)
.attr("ry", 5);*/

var legend = svg.select(".episode:last-child").selectAll(".legend")
.data(function(d) { return d.ages; })
.enter().append("g")
.attr("class", "legend")
.attr("transform", function(d) { return "translate(" + x.rangeBand() / 2 + "," + y((d.y0 + d.y1) / 2) + ")"; });

legend.append("line")
.attr("x2", 10);

legend.append("text")
.attr("x", 13)
.attr("dy", ".35em")
.text(function(d) { return d.name; });

//});

jsFiddle