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Encircling D3's Fisheye Distortion

Except for the code segments that render the magnifying glass (as circle or path), this is essentially a copy of Mike Bostock's Fisheye Distortion example.

The motivation for this was largely aesthetical but also a bit functional. When using the Fisheye as an aid to viewing large datasets, I often find myself experimenting with the degree and radius of the distortion. In such cases, I find it helpful to see the exact reach of the distortion and then decide the best configuration for a particular dataset.

(function() {
d3.fisheye = {
scale: function(scaleType) {
return d3_fisheye_scale(scaleType(), 3, 0);
},
circular: function() {
var radius = 200,
distortion = 2,
k0,
k1,
focus = [0, 0];
function fisheye(d) {
var dx = d.x - focus[0],
dy = d.y - focus[1],
dd = Math.sqrt(dx * dx + dy * dy);
if (!dd || dd >= radius) return {x: d.x, y: d.y, z: 1};
var k = k0 * (1 - Math.exp(-dd * k1)) / dd * .75 + .25;
return {x: focus[0] + dx * k, y: focus[1] + dy * k, z: Math.min(k, 10)};
}
function rescale() {
k0 = Math.exp(distortion);
k0 = k0 / (k0 - 1) * radius;
k1 = distortion / radius;
return fisheye;
}
fisheye.radius = function(_) {
if (!arguments.length) return radius;
radius = +_;
return rescale();
};
fisheye.distortion = function(_) {
if (!arguments.length) return distortion;
distortion = +_;
return rescale();
};
fisheye.focus = function(_) {
if (!arguments.length) return focus;
focus = _;
return fisheye;
};
return rescale();
}
};
function d3_fisheye_scale(scale, d, a) {
function fisheye(_) {
var x = scale(_),
left = x < a,
range = d3.extent(scale.range()),
min = range[0],
max = range[1],
m = left ? a - min : max - a;
if (m == 0) m = max - min;
return (left ? -1 : 1) * m * (d + 1) / (d + (m / Math.abs(x - a))) + a;
}
fisheye.distortion = function(_) {
if (!arguments.length) return d;
d = +_;
return fisheye;
};
fisheye.focus = function(_) {
if (!arguments.length) return a;
a = +_;
return fisheye;
};
fisheye.copy = function() {
return d3_fisheye_scale(scale.copy(), d, a);
};
fisheye.nice = scale.nice;
fisheye.ticks = scale.ticks;
fisheye.tickFormat = scale.tickFormat;
return d3.rebind(fisheye, scale, "domain", "range");
}
})();
<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<TITLE>Encircling D3 Fisheye Distortion</TITLE>
<script type="text/javascript" src="https://d3js.org/d3.v3.min.js"></script>
<script type="text/javascript" src="fisheye.js"></script>
<style>
.background {
fill: none;
pointer-events: all;
}
/*
#chart1 {
width: 960px;
height: 600px;
border: solid 1px #ccc;
}
*/
#chart1 .circle {
stroke: #fff;
stroke-width: 1.5px;
}
#chart1 .link {
stroke: #999;
stroke-opacity: .6;
stroke-width: 1.5px;
}
text {
font: 12px sans-serif;
pointer-events: none;
text-anchor: start;
}
/* magnifier glass as circle */
.lens {
stroke: gray;
stroke-width: 2.0px;
stroke-opacity: 0;
fill: none;
}
/* magnifier glass as path */
.mag {
stroke: gray;
stroke-width: 2.0px;
stroke-opacity: 0;
fill: none;
}
/* magnifier handle as path */
.mag2 {
stroke: black;
stroke-width: 12.0px;
stroke-opacity: 0;
fill: none;
}
</style>
</head>
<body bgcolor="white">
<form style="margin-left: 20px">
<input type="radio" name="wot" id="circle" value="one" />&nbsp;as circle<br/>
<input type="radio" name="wot" id="path" value="two" checked />&nbsp;as path
</form>
<div id="chart1"></div>
<script>
var width = 960,
height = 600;
var color = d3.scale.category20();
var fisheye = d3.fisheye.circular()
.radius(100)
.distortion(5);
var force = d3.layout.force()
.charge(-440)
.linkDistance(60)
.size([width, height]);
var svg = d3.select("#chart1").append("svg")
.attr("width", width)
.attr("height", height);
// magnifier as circle
var lens = svg.append("circle")
.attr("class","lens")
.attr("r", fisheye.radius());;
// magnifier as path
var mag = svg.append("path")
.attr("class", "mag");
// specify angle where magnifier handle should "attach" to body
var omega = 0.78;
// magnifier handle as path
var mag2 = svg.append("path")
.attr("class", "mag2");
/*
svg.append("rect")
.attr("class", "background")
.attr("width", width)
.attr("height", height);
*/
d3.json("miserables.json", function(data) {
var n = data.nodes.length;
force.nodes(data.nodes).links(data.links);
// Initialize the positions deterministically, for better results.
data.nodes.forEach(function(d, i) { d.x = d.y = width / n * i; });
// Run the layout a fixed number of times.
// The ideal number of times scales with graph complexity.
// Of course, don't run too long—you'll hang the page!
force.start();
for (var i = n; i > 0; --i) force.tick();
force.stop();
// Center the nodes in the middle.
var ox = 0, oy = 0;
data.nodes.forEach(function(d) { ox += d.x, oy += d.y; });
ox = ox / n - width / 2, oy = oy / n - height / 2;
data.nodes.forEach(function(d) { d.x -= ox, d.y -= oy; });
var link = svg.selectAll(".link")
.data(data.links)
.enter().append("line")
.attr("class", "link")
.attr("x1", function(d) { return d.source.x; })
.attr("y1", function(d) { return d.source.y; })
.attr("x2", function(d) { return d.target.x; })
.attr("y2", function(d) { return d.target.y; })
.style("stroke-width", function(d) { return Math.sqrt(d.value); });
var node = svg.selectAll(".node")
.data(data.nodes)
.enter().append("g")
.attr("class", "node");
render("path");
function render(shape) {
node.selectAll(".link").remove();
node.selectAll(".circle").remove();
node.selectAll(".text").remove();
lens.style("stroke-opacity", shape == "circle" ? 1 : 0);
mag.style("stroke-opacity", shape == "path" ? 1 : 0);
mag2.style("stroke-opacity", shape == "path" ? 1 : 0);
var nodeEnter = node
.append("circle")
.attr("class", "circle")
.attr("cx", function(d) { return d.x; })
.attr("cy", function(d) { return d.y; })
.attr("r", 6)
.style("fill", function(d) { return color(d.group); })
.call(force.drag);
var text = node.append("text")
.attr("class", "text")
.attr("dy", function(d) { return d.y; })
.attr("dx", function(d) { return d.x; })
.text(function(d) { return d.name; });
node.append("title")
.text(function(d) { return d.name; });
svg.on("mousemove", function() {
fisheye.focus(d3.mouse(this));
var mouseX = d3.mouse(this)[0];
var mouseY = d3.mouse(this)[1];
var r = fisheye.radius();
if (shape == "circle") {
// display magnifier as circle
lens
.attr("cx", mouseX)
.attr("cy", mouseY);
}
else {
// path for magnifier
var magPath = "M " + mouseX + "," + mouseY + " m -" + r + ", 0 a " + r + "," + r + " 0 1,0 " + (r * 2) + ",0 a " + r + "," + r + " 0 1,0 -" + (r * 2) + ",0";
// point in circumference to attach magnifier handle
var x1 = mouseX + r * Math.sin(omega);
var y1 = mouseY + r * Math.cos(omega);
// path for magnifier's handle
var mag2Path = "M " + (x1 + 2) + "," + (y1 + 2) + " L" + (mouseX + r * 1.7) + "," + (mouseY + r * 1.7);
// display magnifier as path
mag.attr("d", magPath);
// display magnifier handle as path
mag2.attr("d", mag2Path);
};
nodeEnter.each(function(d) { d.fisheye = fisheye(d); })
.attr("cx", function(d) { return d.fisheye.x; })
.attr("cy", function(d) { return d.fisheye.y; })
.attr("r", function(d) { return d.fisheye.z * 4.5; });
text.attr("dx", function(d) { return d.fisheye.x; })
.attr("dy", function(d) { return d.fisheye.y; });
link.attr("x1", function(d) { return d.source.fisheye.x; })
.attr("y1", function(d) { return d.source.fisheye.y; })
.attr("x2", function(d) { return d.target.fisheye.x; })
.attr("y2", function(d) { return d.target.fisheye.y; });
});
}
d3.select("#circle").on("click", function () { render("circle");});
d3.select("#path").on("click", function () { render("path");});
})
</script>
</body>
</html>
{
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{"name":"Napoleon","group":1},
{"name":"Mlle.Baptistine","group":1},
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{"name":"Thenardier","group":4},
{"name":"Cosette","group":5},
{"name":"Javert","group":4},
{"name":"Fauchelevent","group":0},
{"name":"Bamatabois","group":2},
{"name":"Perpetue","group":3},
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{"name":"Scaufflaire","group":2},
{"name":"Woman1","group":2},
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{"name":"Gavroche","group":8},
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{"name":"Marius","group":8},
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{"name":"Mabeuf","group":8},
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{"name":"Combeferre","group":8},
{"name":"Prouvaire","group":8},
{"name":"Feuilly","group":8},
{"name":"Courfeyrac","group":8},
{"name":"Bahorel","group":8},
{"name":"Bossuet","group":8},
{"name":"Joly","group":8},
{"name":"Grantaire","group":8},
{"name":"MotherPlutarch","group":9},
{"name":"Gueulemer","group":4},
{"name":"Babet","group":4},
{"name":"Claquesous","group":4},
{"name":"Montparnasse","group":4},
{"name":"Toussaint","group":5},
{"name":"Child1","group":10},
{"name":"Child2","group":10},
{"name":"Brujon","group":4},
{"name":"Mme.Hucheloup","group":8}
],
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]
}
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