Label placement in d3 radial bar chart

Question

Here in my d3 radial chart, I am trying to get the label text just above the segment arcs instead of keeping outside the outer circle.

Fiddle

    var width = 360,
    height = 300,
    barHeight = height / 2 - 40;

    var formatNumber = d3.format("s");

    var color = d3.scale.ordinal()
    .range(["#F15D5D","#FAD64B"]);

    var svg = d3.select('#chart').append("svg")
    .attr("width", width)
    .attr("height", height)
    .attr('class','radial')
    .append("g")
    .attr("transform", "translate(" + width/2 + "," + height/2 + ")");

    var data = [{
        "name": "ABC",
        "value":4
    },
    {
        "name": "XYZ",
        "value":5
    },{
        "name": "DEF",
        "value":2
    },
    {
        "name": "GHI",
        "value":3
    },{
        "name": "JKL",
        "value":1
    }];

    data.sort(function(a,b) { return b.value - a.value; });

    var extent = [0, d3.max(data, d=>d.value)];
    var barScale = d3.scale.linear()
    .domain(extent)
    .range([0, barHeight]);

    var keys = data.map(function(d,i) { return d.name; });
    var numBars = keys.length;


    // X scale
    var x = d3.scale.linear()
    .domain(extent)
    .range([0, -barHeight]);

    // X axis
    var xAxis = d3.svg.axis()
    .scale(x).orient("left")
    .ticks(3)
    .tickFormat(formatNumber);

    // Inner circles
    var circles = svg.selectAll("circle")
    .data(x.ticks(5))
    .enter().append("circle")
    .attr("r", function(d) {return barScale(d);})
    .style("fill", "none")
    //.style("stroke", "black")
    //.style("stroke-dasharray", "2,2")
    .style("stroke-width",".5px");

    // Create arcs
    var arc = d3.svg.arc()
    .startAngle(function(d,i) { 
     var a = (i * 2 * Math.PI) / numBars;
     var b = ((i + 1) * 2 * Math.PI) / numBars;
     var d = (b-a) / 4;
     var x = a+d;
     var y = b-d;

     return x;//(i * 2 * Math.PI) / numBars; 
    })
      .endAngle(function(d,i) { 
    var a = (i * 2 * Math.PI) / numBars;
    var b = ((i + 1) * 2 * Math.PI) / numBars;
    var d = (b-a) / 4;
    var x = a+d;
    var y = b-d;
    return y;//((i + 1) * 2 * Math.PI) / numBars; 
  })
    .innerRadius(0);

   // Render colored arcs
    var segments = svg.selectAll("path")
    .data(data)
    .enter().append("path")
    .each(function(d) { d.outerRadius = 0; })
    .style("fill", function (d) { return color(d.name); })
    .attr("d", arc);

   // Animate segments
    segments.transition().ease("elastic").duration(1000).delay(function(d,i) {return (25-i)*50;})
    .attrTween("d", function(d,index) {
        var i = d3.interpolate(d.outerRadius, barScale(+d.value));
        return function(t) { d.outerRadius = i(t); return arc(d,index); };
    });

   // Outer circle
    svg.append("circle")
    .attr("r", barHeight)
    .classed("outer", true)
    .style("fill", "none")
    //.style("stroke", "black")
    .style("stroke-width",".5px");

   // Apply x axis
    svg.append("g")
    .attr("class", "x axis")
    .call(xAxis);

    // Labels
   var labelRadius = barHeight * 1.025;

var labels = svg.append("g")
    .classed("labels", true);

labels.append("def")
    .append("path")
    .attr("id", "label-path")
    .attr("d", "m0 " + -labelRadius + " a" + labelRadius + " " + labelRadius + " 0 1,1 -0.01 0");

labels.selectAll("text")
    .data(keys)
    .enter().append("text")
    .style("text-anchor", "middle")
    .style("font-weight","bold")
    .style("fill", function(d, i) {return "#555";})
    .append("textPath")
    .attr("xlink:href", "#label-path")
    .attr("startOffset", function(d, i) {return i * 100 / numBars + 50 / numBars + '%';})
    .text(function(d) {return d.toUpperCase(); });

Answer 1

We can set the position of the <defs> 's paths using the same data you used to create the arcs.

First, let's create an enter selection:

var labels = svg.selectAll("foo")
    .data(data)
    .enter()
    .append("g")
    .classed("labels", true);

Then, we append the paths using the barScale for each value (hardcoded padding of 4px here):

labels.append("def")
    .append("path")
    .attr("id", (d, i) => "label-path" + i)
    .attr("d", d => "m0 " + -(barScale(d.value) + 4) +
        " a" + (barScale(d.value) + 4) + " " +
        (barScale(d.value) + 4) + " 0 1,1 -0.01 0");

Please notice that we have to use unique IDs. Then, we change the IDs in the text-paths:

.attr("xlink:href", (d, i) => "#label-path" + i)

Here is your updated fiddle: https://jsfiddle.net/qt3e0rex/

And the same code in the Stack snippet:

 var width = 360, height = 300, barHeight = height / 2 - 40; var formatNumber = d3.format("s"); var color = d3.scale.ordinal() .range(["#F15D5D", "#FAD64B"]); var svg = d3.select('body').append("svg") .attr("width", width) .attr("height", height) .attr('class', 'radial') .append("g") .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")"); var data = [{ "name": "ABC", "value": 4 }, { "name": "XYZ", "value": 5 }, { "name": "DEF", "value": 2 }, { "name": "GHI", "value": 3 }, { "name": "JKL", "value": 1 }]; data.sort(function(a, b) { return b.value - a.value; }); var extent = [0, d3.max(data, d => d.value)]; var barScale = d3.scale.linear() .domain(extent) .range([0, barHeight]); var keys = data.map(function(d, i) { return d.name; }); var numBars = keys.length; // X scale var x = d3.scale.linear() .domain(extent) .range([0, -barHeight]); // X axis var xAxis = d3.svg.axis() .scale(x).orient("left") .ticks(3) .tickFormat(formatNumber); // Inner circles var circles = svg.selectAll("circle") .data(x.ticks(5)) .enter().append("circle") .attr("r", function(d) { return barScale(d); }) .style("fill", "none") //.style("stroke", "black") //.style("stroke-dasharray", "2,2") .style("stroke-width", ".5px"); // Create arcs var arc = d3.svg.arc() .startAngle(function(d, i) { var a = (i * 2 * Math.PI) / numBars; var b = ((i + 1) * 2 * Math.PI) / numBars; var d = (b - a) / 4; var x = a + d; var y = b - d; return x; //(i * 2 * Math.PI) / numBars; }) .endAngle(function(d, i) { var a = (i * 2 * Math.PI) / numBars; var b = ((i + 1) * 2 * Math.PI) / numBars; var d = (b - a) / 4; var x = a + d; var y = b - d; return y; //((i + 1) * 2 * Math.PI) / numBars; }) .innerRadius(0); // Render colored arcs var segments = svg.selectAll("path") .data(data) .enter().append("path") .each(function(d) { d.outerRadius = 0; }) .style("fill", function(d) { return color(d.name); }) .attr("d", arc); // Animate segments segments.transition().ease("elastic").duration(1000).delay(function(d, i) { return (25 - i) * 50; }) .attrTween("d", function(d, index) { var i = d3.interpolate(d.outerRadius, barScale(+d.value)); return function(t) { d.outerRadius = i(t); return arc(d, index); }; }); // Outer circle svg.append("circle") .attr("r", barHeight) .classed("outer", true) .style("fill", "none") //.style("stroke", "black") .style("stroke-width", ".5px"); // Apply x axis svg.append("g") .attr("class", "x axis") .call(xAxis); // Labels var labelRadius = barHeight * 1.025; var labels = svg.selectAll("foo") .data(data) .enter() .append("g") .classed("labels", true); labels.append("def") .append("path") .attr("id", (d, i) => "label-path" + i) .attr("d", d => "m0 " + -(barScale(d.value) + 4) + " a" + (barScale(d.value) + 4) + " " + (barScale(d.value) + 4) + " 0 1,1 -0.01 0"); labels.append("text") .style("text-anchor", "middle") .style("font-weight", "bold") .style("fill", function(d, i) { return "#555"; }) .append("textPath") .attr("xlink:href", (d, i) => "#label-path" + i) .attr("startOffset", function(d, i) { return i * 100 / numBars + 50 / numBars + '%'; }) .text(function(d) { return d.name.toUpperCase(); }); 

 body { background-color:#fff; } .axis path, .axis line { fill: none; shape-rendering: crispEdges; } .x.axis path { display: none; } .tick text, line { display:none; } circle { stroke:#ccc; } 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.4.11/d3.min.js"></script>