This multi-line chart uses an invisible Voronoi tessellation to handle mouseover; the closest point to the mouse on any line is highlighted. Click the checkbox in the top-right to toggle the visibility of the Voronoi overlay.
forked from mbostock's block: Multi-Line Voronoi
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<meta charset="utf-8">
<style>
.axis--y path {
display: none;
}
.cities {
fill: none;
stroke: #aaa;
stroke-linejoin: round;
stroke-linecap: round;
stroke-width: 1.5px;
}
.city--hover {
stroke: #000;
}
.focus text {
text-anchor: middle;
text-shadow: 0 1px 0 #fff, 1px 0 0 #fff, 0 -1px 0 #fff, -1px 0 0 #fff;
}
.voronoi path {
fill: none;
pointer-events: all;
}
.voronoi--show path {
stroke: red;
stroke-opacity: 0.2;
}
#form {
position: absolute;
top: 20px;
right: 30px;
}
</style>
<svg width="960" height="500"></svg>
<label id="form" for="show-voronoi">
Show Voronoi
<input type="checkbox" id="show-voronoi" disabled>
</label>
<script src="//d3js.org/d3.v4.min.js"></script>
<script>
var months,
monthKeys,
monthParse = d3.timeParse("%Y-%m");
var svg = d3.select("svg"),
margin = {top: 20, right: 30, bottom: 30, left: 40},
width = svg.attr("width") - margin.left - margin.right,
height = svg.attr("height") - margin.top - margin.bottom,
g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")");
var x = d3.scaleTime()
.range([0, width]);
var y = d3.scaleLinear()
.range([height, 0]);
var voronoi = d3.voronoi()
.x(function(d) { return x(d.date); })
.y(function(d) { return y(d.value); })
.extent([[-margin.left, -margin.top], [width + margin.right, height + margin.bottom]]);
var line = d3.line()
.x(function(d) { return x(d.date); })
.y(function(d) { return y(d.value); });
d3.tsv("unemployment.tsv", type, function(error, data) {
if (error) throw error;
console.log('data',data)
x.domain(d3.extent(months));
y.domain([0, d3.max(data, function(c) { return d3.max(c.values, function(d) { return d.value; }); })]).nice();
g.append("g")
.attr("class", "axis axis--x")
.attr("transform", "translate(0," + height + ")")
.call(d3.axisBottom(x));
g.append("g")
.attr("class", "axis axis--y")
.call(d3.axisLeft(y).ticks(10, "%"))
.append("text")
.attr("x", 4)
.attr("y", 0.5)
.attr("dy", "0.32em")
.style("text-anchor", "start")
.style("fill", "#000")
.style("font-weight", "bold")
.text("Unemployment Rate");
g.append("g")
.attr("class", "cities")
.selectAll("path")
.data(data)
.enter().append("path")
.attr("d", function(d) { d.line = this; return line(d.values); });
var focus = g.append("g")
.attr("transform", "translate(-100,-100)")
.attr("class", "focus");
focus.append("circle")
.attr("r", 3.5);
focus.append("text")
.attr("y", -10);
var voronoiGroup = g.append("g")
.attr("class", "voronoi");
voronoiGroup.selectAll("path")
.data(voronoi.polygons(d3.merge(data.map(function(d) { console.log(d); return d.values; }))))
.enter().append("path")
.attr("d", function(d) { return d ? "M" + d.join("L") + "Z" : null; })
.on("mouseover", mouseover)
.on("mouseout", mouseout);
d3.select("#show-voronoi")
.property("disabled", false)
.on("change", function() { voronoiGroup.classed("voronoi--show", this.checked); });
function mouseover(d) {
d3.select(d.data.city.line).classed("city--hover", true);
d.data.city.line.parentNode.appendChild(d.data.city.line);
focus.attr("transform", "translate(" + x(d.data.date) + "," + y(d.data.value) + ")");
focus.select("text").text(d.data.city.name);
}
function mouseout(d) {
d3.select(d.data.city.line).classed("city--hover", false);
focus.attr("transform", "translate(-100,-100)");
}
});
function type(d, i, columns) {
if (!months) monthKeys = columns.slice(1), months = monthKeys.map(monthParse);
var c = {name: d.name.replace(/ (msa|necta div|met necta|met div)$/i, ""), values: null};
c.values = monthKeys.map(function(k, i) { return {city: c, date: months[i], value: d[k] / 100}; });
return c;
}
</script>
https://d3js.org/d3.v4.min.js