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@ajfarkas ajfarkas/README.md
Last active Jun 2, 2016

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Tool Tips for Line Graph

Tool Tips

An SVG hovering element that shows the value under the mouse point. This example generates random Y-axis values (-100 to 100) across a 120-second interval (X-axis).

A good amount of this code is for centering text, which I plan to streamline at some point.

var randomData = []
// create a bunch of values for the graph
function createrandomData() {
var now = Date.now()
for(var i = 0; i < 120; i++) {
randomData[i] = {
yValue: (Math.random() - 0.5) * 200,
time: now + (i * 1000)
}
}
}
function createGraph() {
createrandomData()
// define plot boundaries
var width = 300,
height = 60
var margin = {
top: 0,
right: 50,
bottom: 5,
left: 50
}
var plot = {
width: width - margin.right - margin.left,
height: height - margin.top - margin.bottom
}
// x-axis is time
var x = d3.time.scale()
.range([0, plot.width])
// y-axis is numerical
var y = d3.scale.linear()
.range([plot.height, 0])
// set axis scales
var xAxis = d3.svg.axis()
.scale(x)
.orient('bottom')
.tickFormat(d3.time.format('%M:%S'))
.tickSize(0, 0).ticks(6)
var yAxis = d3.svg.axis()
.scale(y)
.orient('left')
.tickSize(0, 0).ticks(3)
x.domain([randomData[0].time, randomData[randomData.length - 1].time])
y.domain([-100, 100])
var line = d3.svg.line()
.x(function(d) { return x(parseInt(d.time)) })
.y(function(d) { return y(d.yValue) })
// make the graph
var svg = d3.select('#graph')
var graph = undefined
if (d3.select('.graph-g').empty()) {
graph = svg.append('g')
.attr('class', 'graph-g')
.attr('width', plot.width)
.attr('height', plot.height)
.attr('transform', 'translate(' + margin.left + ',' + margin.top + ')')
//add axes
graph.append('g')
.attr('class', 'x axis')
.attr('transform', 'translate(0,' + plot.height + ')')
.call(xAxis)
graph.append('g')
.attr('class', 'y axis')
.call(yAxis)
.append('text')
.attr('transform', 'rotate(-90)')
.attr('dx', (0 - plot.height / 2))
.attr('dy', '-2.8em')
.style('text-anchor', 'middle')
.text('Value')
} else {
graph = d3.select('.graph-g')
}
//add data line
graph.append('path')
.datum(randomData)
.attr('class', 'line')
.attr('d', line)
// Tooltip for yValue value at point of hover on line.
// create tooltip
var tip = graph.append('g')
.attr('class', 'tool-tip')
.style('visibility', 'hidden')
var tipBg = tip.append('rect')
.attr('class', 'tool-tipBG')
var tipTitle = tip.append('text')
.attr('x', '0')
.attr('y', '0')
.attr('class', 'tip-title')
.text('00:00')
var titleBB = tipTitle.node().getBBox()
var tipVal = tip.append('text')
.attr('x', '0')
.attr('y', '0')
.attr('class', 'tip-number')
.text('+100')
tipVal
.attr('y', tipVal.node().getBBox().height - 2)
.attr('x', tipVal.node().getBBox().width - 3)
var valBB = tipVal.node().getBBox()
var tipText = tip.append('text')
.attr('x', valBB.width)
.attr('y', valBB.height - 2)
.attr('class', 'tip-text')
.text('sprokets')
var textBB = tipText.node().getBBox()
tipBg
.attr('x', '0')
.attr('y', -titleBB.height - 3)
.attr('dx', '-3')
.attr('rx', '4')
.attr('ry', '4')
.attr('width',
Math.max(valBB.width + textBB.width + 7, titleBB.width + 7)
)
.attr('height', titleBB.height + valBB.height + 6)
var bgBB = tipBg.node().getBBox()
tipTitle.attr('dx', bgBB.width/2)
tipTitle.attr('dy', -2)
tipVal.attr('dx', (bgBB.width - valBB.width - textBB.width)/2 )
tipText.attr('dx', (bgBB.width - valBB.width - textBB.width)/2 - 2)
tip.append('path')
.attr('class', 'tool-tipPoint')
.attr('d', 'M-6,0L6,0L0,8Z')
.attr('transform', 'translate('+bgBB.width/2+', '+(valBB.height+2.8)+')')
// set bisection data
var bisect = d3.bisector(function(d) { return d.time }).left
// show/hide tooltip
function updateTipData() {
var x0 = x.invert(d3.mouse(this)[0])
var i = bisect(randomData, x0, 1)
// find the closest value to the mouse
var dPre = randomData[i - 1],
dPost = randomData[i]
if (typeof dPost === 'undefined') {
return false
}
var d = x0 - dPre.time < dPost.time - x0
? dPre
: dPost
// apply value to tip text (with + for pos, - for neg, and null for 0)
tipVal.text(function() {
return (d.yValue > 0
? '+'+Math.round(d.yValue)
: Math.round(d.yValue)
)
})
tipTitle.text(function() {
var time = new Date(d.time)
return ('0'+time.getMinutes()).slice(-2)+':'+('0'+time.getSeconds()).slice(-2)
})
// show tip at nearest data point
tip.attr('transform', 'translate('+( x(d.time) - bgBB.width/2)+','+( y(d.yValue) - bgBB.height/2 - 9 )+')')
}
graph.on('mouseover', function() { tip.style('visibility', 'visible') })
d3.select('.line').on('mousemove', updateTipData)
svg.on('mouseout', function() { tip.style('visibility', 'hidden') })
}
// make it so
createGraph()
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
<link href="styles.css" rel="stylesheet" type="text/css"/>
<title>Tool Tips</title>
</head>
<body>
<svg id="graph" viewBox="0 0 300 60"></svg>
</body>
<script src="graph.js" rel="javascript" type="text/javascript"></script>
</html>
#graph {
width: 960px;
height: 480px;
}
.line {
fill: none;
stroke: black;
}
text { font-size: 0.5rem; }
.tool-tipBG { fill: gold; }
.tool-tipPoint { fill: gold; }
.tip-title { text-anchor: middle; }
.tip-number { text-anchor: end; }
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