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Last active Mar 10, 2016
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Inline Labels
license: gpl-3.0

This example shows how to implement Ann K. Emery’s technique of placings labels directly on top of a line in D3 4.0 Alpha.

To construct the multi-series line chart, the data is first transformed into separate arrays for each series. (The series names are automatically derived from the columns in the TSV file, thanks to a new dsv.parse feature.)

var series = data.columns.slice(1).map(function(key) {
  return data.map(function(d) {
    return {
      key: key,
      date: d.date,
      value: d[key]
    };
  });
});

A label is rendered for each point in each series. Beneath this label, a white rectangle is added, whose size and position is computed automatically using element.getBBox plus a little bit of padding. The resulting label is thus legible. The last label for each series gets an additional tspan to show the series name.

date Apples Bananas
2009 130 40
2010 137 58
2011 166 97
2012 154 117
2013 99 99
2014 187 120
2015 189 84
<!DOCTYPE html>
<meta charset="utf-8">
<style>
text {
font: 10px sans-serif;
}
.axis path,
.axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.line {
fill: none;
stroke-width: 1.5px;
}
.label {
text-anchor: middle;
}
.label rect {
fill: white;
}
.label-key {
font-weight: bold;
}
</style>
<svg width="960" height="500"></svg>
<script src="//d3js.org/d3.v4.0.0-alpha.9.min.js"></script>
<script>
var parseTime = d3.timeParse("%Y");
var svg = d3.select("svg");
var margin = {top: 30, right: 50, bottom: 30, left: 30},
width = +svg.attr("width") - margin.left - margin.right,
height = +svg.attr("height") - margin.top - margin.bottom,
labelPadding = 3;
var g = svg.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");
d3.requestTsv("data.tsv", function(d) {
d.date = parseTime(d.date);
for (var k in d) if (k !== "date") d[k] = +d[k];
return d;
}, function(error, data) {
if (error) throw error;
var series = data.columns.slice(1).map(function(key) {
return data.map(function(d) {
return {
key: key,
date: d.date,
value: d[key]
};
});
});
var x = d3.scaleTime()
.domain([data[0].date, data[data.length - 1].date])
.range([0, width]);
var y = d3.scaleLinear()
.domain([0, d3.max(series, function(s) { return d3.max(s, function(d) { return d.value; }); })])
.range([height, 0]);
var z = d3.scaleCategory10();
g.append("g")
.attr("class", "axis axis--x")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x));
var serie = g.selectAll(".serie")
.data(series)
.enter().append("g")
.attr("class", "serie");
serie.append("path")
.attr("class", "line")
.style("stroke", function(d) { return z(d[0].key); })
.attr("d", d3.line()
.x(function(d) { return x(d.date); })
.y(function(d) { return y(d.value); }));
var label = serie.selectAll(".label")
.data(function(d) { return d; })
.enter().append("g")
.attr("class", "label")
.attr("transform", function(d, i) { return "translate(" + x(d.date) + "," + y(d.value) + ")"; });
label.append("text")
.attr("dy", ".35em")
.text(function(d) { return d.value; })
.filter(function(d, i) { return i === data.length - 1; })
.append("tspan")
.attr("class", "label-key")
.text(function(d) { return " " + d.key; });
label.append("rect", "text")
.datum(function() { return this.nextSibling.getBBox(); })
.attr("x", function(d) { return d.x - labelPadding; })
.attr("y", function(d) { return d.y - labelPadding; })
.attr("width", function(d) { return d.width + 2 * labelPadding; })
.attr("height", function(d) { return d.height + 2 * labelPadding; });
});
</script>
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