Learning how to use d3-drag for an interactive "Make a guess" connected dot plot. Dragging is limited to the x-axis and the ends of the line cannot cross over (i.e. their positions cannot be switched). Clicking reset returns the dots to their original positions.
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August 3, 2017 16:14
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Draggable Connected Dot Plot
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license: mit |
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<!DOCTYPE html> | |
<head> | |
<meta charset="utf-8"> | |
<script src="https://d3js.org/d3.v4.min.js"></script> | |
<style> | |
.dot { | |
fill: white; | |
stroke: black; | |
} | |
.active { | |
stroke: red; | |
} | |
body { | |
font-family: monospace; | |
} | |
a { | |
position: absolute; | |
top: 20px; | |
left: 20px; | |
} | |
</style> | |
</head> | |
<body> | |
<a href="#" class="reset-btn">Reset</a> | |
<script> | |
var margin = {top: 0, right: 0, bottom: 0, left: 0}; | |
var width = 960 - margin.left - margin.right, | |
height = 500 - margin.top - margin.bottom; | |
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 + ")"); | |
var radius = 20, | |
strokewidth = 5; | |
var te = d3.easeCubic; | |
var dots = [ | |
{ | |
type: "min", | |
colour: "white", | |
x: width / 4, | |
y: height / 2 | |
}, | |
{ | |
type: "median", | |
colour: "grey", | |
x: width / 2, | |
y: height / 2 | |
}, | |
{ | |
type: "max", | |
colour: "black", | |
x: width * 3 / 4, | |
y: height / 2 | |
}]; | |
var dotsoriginal = JSON.parse(JSON.stringify(dots)); | |
var dragbehaviour = d3.drag() | |
.on("start", dragstarted) | |
.on("drag", dragged) | |
.on("end", dragended); | |
var labels = svg.selectAll("text") | |
.data(dots) | |
.enter().append("text") | |
.attr("x", function(d) { return d.x }) | |
.attr("y", function(d) { | |
return height / 2 + (d.type == "min" || d.type == "max" ? 60 : -50) | |
}) | |
.attr("text-anchor", "middle") | |
.text(function(d) { return "(" + d.x + ", " + d.y + ")" }); | |
var lineGenerator = d3.line() | |
.x(function(d) { return d.x + (d.type == "min" ? radius : -radius)}) | |
.y(function(d) { return d.y }); | |
var pathString = function() { return lineGenerator(dots) }; | |
var line = svg.append("path") | |
.attr("class", "line") | |
.attr("d", pathString) | |
.attr("stroke", "black") | |
.style("stroke-width", strokewidth); | |
var circles = svg.selectAll("circle") | |
.data(dots) | |
.enter().append("circle") | |
.attr("class", "dot") | |
.attr("cx", function(d) { return d.x; }) | |
.attr("cy", function(d) { return d.y; }) | |
.attr("r", radius) | |
.style("fill", function(d) { return d.colour }) | |
.style("stroke-width", strokewidth) | |
.call(dragbehaviour); | |
function dragstarted(d) { | |
d3.select(this) | |
.classed("active", true); | |
} | |
function dragged(d) { | |
var minX, maxX; | |
if (d.type == "min") { | |
minX = radius + strokewidth; | |
maxX = dots[1].x - (radius * 2) - strokewidth; | |
} else if (d.type == "median") { | |
minX = dots[0].x + (radius * 2) + strokewidth; | |
maxX = dots[2].x - (radius * 2) - strokewidth; | |
} else { | |
minX = dots[1].x + (radius * 2) + strokewidth; | |
maxX = width - radius - strokewidth; | |
} | |
d3.select(this) | |
.attr("cx", d.x = Math.max(minX, Math.min(maxX, d3.event.x))); | |
labels | |
.attr("x", function(d) { return d.x }) | |
.text(function(d) { return "(" + d.x + ", " + d.y + ")" }); | |
line.attr("d", pathString); | |
} | |
function dragended(d) { | |
d3.select(this) | |
.classed("active", false); | |
} | |
d3.select(".reset-btn") | |
.on("click", function(d) { | |
d3.event.preventDefault(); | |
dots = dotsoriginal; | |
dotsoriginal = JSON.parse(JSON.stringify(dots)); | |
line.transition() | |
.duration(500) | |
.ease(te) | |
.attr("d", pathString); | |
circles.data(dots).transition() | |
.duration(500) | |
.ease(te) | |
.attr("cx", function(d) { return d.x; }); | |
labels.data(dots).transition() | |
.duration(500) | |
.ease(te) | |
.attr("x", function(d) { return d.x; }) | |
.text(function(d) { return "(" + d.x + ", " + d.y + ")" }); | |
}); | |
</script> | |
</body> |
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