Using data from the US Census, this visualization displays popular names that have historically been androgynous.
Control points are not intersected by the path for several non-linear interpolations for lines ("basis" in this case). Because of this, point tracking for non-linear lines should be calculated from the svg-path rather than from the d3-scales. Mike Bostock has two examples showing how to do this with a single path. This gist shows one approach for point tracking with multiple paths. Other approaches are shown here and here.
This approach uses a combination of precomputed voronoi tessellations and on-the-fly closestPoint to determine which line and point to highlight. The voronoi tessellations determine the line, which the on-the-fly closestPoint determines the point. Notedly, the voronoi tessellations are computed using the coordinates producted by the linear scale, rather than the non-linear scale ("basis" here). For this visualization, incorrect line selection does not occur as a result of this under-the-hood inaccuracy. YMMV.
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<meta charset="utf-8">
<style>
body {
width: 960px;
margin: auto;
position: relative;
}
svg {
font: 11px "Helvetica Neue", Helvetica, Arial, sans-serif;
}
.axis path,
.axis line {
fill: none;
stroke: #000;
shape-rendering: crispEdges;
}
.axis--y path {
display: none;
}
.androgs {
fill: none;
stroke: #aaa;
stroke-linejoin: round;
stroke-linecap: round;
stroke-width: 1.5px;
}
.androg--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: .2;
}
#form {
position: absolute;
top: 20px;
right: 30px;
}
</style>
<label id="form" for="show-voronoi">
Show Voronoi
<input type="checkbox" id="show-voronoi" disabled>
</label>
<script src="https://d3js.org/d3.v3.js"></script>
<script>
var years,
yearFormat = d3.time.format("%Y");
var margin = {top: 20, right: 30, bottom: 30, left: 40},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;
var x = d3.time.scale()
.range([0, width]);
var y = d3.scale.linear()
.range([height, 0]);
var color = d3.scale.category20();
var voronoi = d3.geom.voronoi()
.x(function(d) { return x(d.date); })
.y(function(d) { return y(d.value); })
.clipExtent([[-margin.left, -margin.top], [width + margin.right, height + margin.bottom]]);
var line = d3.svg.line()
.interpolate("basis")
.x(function(d) { return x(d.date); })
.y(function(d) { return y(d.value); });
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("steady_andro.csv", type, function(error, androgs) {
x.domain(d3.extent(years));
y.domain([0, d3.max(androgs, function(c) { return d3.max(c.values, function(d) { return d.value; }); })]).nice();
svg.append("g")
.attr("class", "axis axis--x")
.attr("transform", "translate(0," + height + ")")
.call(d3.svg.axis()
.scale(x)
.orient("bottom"));
svg.append("g")
.attr("class", "axis axis--y")
.call(d3.svg.axis()
.scale(y)
.orient("left")
.ticks(10, "%"))
.append("text")
.attr("x", 4)
.attr("dy", ".32em")
.style("font-weight", "bold")
.text("Percent Female");
svg.append("g")
.attr("class", "androgs")
.selectAll("path")
.data(androgs)
.enter().append("path")
.attr("d", function(d) { d.line = this;
return line(d.values);});
var focus = svg.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 = svg.append("g")
.attr("class", "voronoi");
voronoiGroup.selectAll("path")
.data(voronoi(d3.nest()
.key(function(d) { // p = closestPoint(d.androg.line, [x(d.date), y(d.value)]);
// return p[0] + "," + p[1];
return x(d.date) + "," + y(d.value); })
.rollup(function(v) { return v[0]; })
.entries(d3.merge(androgs.map(function(d) { return d.values; })))
.map(function(d) { return d.values; })))
.enter().append("path")
.attr("d", function(d) { return "M" + d.join("L") + "Z"; })
.datum(function(d) { return d.point; })
.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) {
p = closestPoint(d.androg.line, d3.mouse(this));
d3.select(d.androg.line).classed("androg--hover", true);
d.androg.line.parentNode.appendChild(d.androg.line);
focus.attr("transform", "translate(" + p[0] + "," + p[1] + ")");
focus.select("text").text(d.androg.name + ": " + d.value.slice(0, 4));
}
function mouseout(d) {
d3.select(d.androg.line).classed("androg--hover", false);
focus.attr("transform", "translate(-100,-100)");
}
});
function closestPoint(pathNode, point) {
var pathLength = pathNode.getTotalLength(),
numberOfItems = pathNode.getPathSegAtLength(pathLength),
precision = (pathLength / numberOfItems) * .5,
best,
bestLength,
bestDistance = Infinity;
// linear scan for coarse approximation
for (var scan, scanLength = 0, scanDistance; scanLength <= pathLength; scanLength += precision) {
if ((scanDistance = distance2(scan = pathNode.getPointAtLength(scanLength))) < bestDistance) {
best = scan, bestLength = scanLength, bestDistance = scanDistance;
}
}
// binary search for precise estimate
precision *= .5;
while (precision > .5) {
var before,
after,
beforeLength,
afterLength,
beforeDistance,
afterDistance;
if ((beforeLength = bestLength - precision) >= 0 && (beforeDistance = distance2(before = pathNode.getPointAtLength(beforeLength))) < bestDistance) {
best = before, bestLength = beforeLength, bestDistance = beforeDistance;
} else if ((afterLength = bestLength + precision) <= pathLength && (afterDistance = distance2(after = pathNode.getPointAtLength(afterLength))) < bestDistance) {
best = after, bestLength = afterLength, bestDistance = afterDistance;
} else {
precision *= .5;
}
}
best = [best.x, best.y];
best.distance = Math.sqrt(bestDistance);
return best;
function distance2(p) {
var dx = p.x - point[0],
dy = p.y - point[1];
return dx * dx + dy * dy;
}
}
function type(d, i) {
if (!i) years = Object.keys(d).map(yearFormat.parse).filter(Number);
var androg = {
name: d.name.replace(/ (msa|necta div|met necta|met div)$/i, ""),
values: null
};
androg.values = years.map(function(m) {
return {
androg: androg,
date: m,
value: d[yearFormat(m)]
};
});
return androg;
}
</script>
Modified http://d3js.org/d3.v3.js to a secure url
https://d3js.org/d3.v3.js