D3是目前最流行的JavaScript可视化图表库之一，D3的图表类型非常丰富，并且支持SVG格式，因此应用十分广泛，也有很多图表插件基于D3开发，比如MetricsGraphics.js，在D3上构建的数据图表非常强大。
D3的特点
允许绑定任意数据到DOM，将数据驱动转换应用到Document中。
不仅可以创建精美的HTML表格，而且可以绘制折线图、柱形图和饼图等数据图表。
支持SVG，在Web页面上渲染毫无压力。
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D3的使用方法
关于D3的具体用法，可以看D3图形库API参考这篇文章。本文主要对介绍一些经典图表的实现效果及代码。
index.html代码：
<!DOCTYPE html>
<meta charset="utf-8">
<style>
svg {
font: 10px sans-serif
}
.y.axis path {
display: none
}
.y.axis line {
stroke: #fff
stroke-opacity: .2
shape-rendering: crispEdges
}
.y.axis .zero line {
stroke: #000
stroke-opacity: 1
}
.title {
font: 300 78px Helvetica Neue
fill: #666
}
.birthyear,
.age {
text-anchor: middle
}
.birthyear {
fill: #fff
}
rect {
fill-opacity: .6
fill: #e377c2
}
rect:first-child {
fill: #1f77b4
}
</style>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script>
var margin = {top: 20, right: 40, bottom: 30, left: 20},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom,
barWidth = Math.floor(width / 19) - 1
var x = d3.scale.linear()
.range([barWidth / 2, width - barWidth / 2])
var y = d3.scale.linear()
.range([height, 0])
var yAxis = d3.svg.axis()
.scale(y)
.orient("right")
.tickSize(-width)
.tickFormat(function(d) { return Math.round(d / 1e6) + "M" })
// An SVG element with a bottom-right origin.
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 + ")")
// A sliding container to hold the bars by birthyear.
var birthyears = svg.append("g")
.attr("class", "birthyears")
// A label for the current year.
var title = svg.append("text")
.attr("class", "title")
.attr("dy", ".71em")
.text(2000)
d3.csv("population.csv", function(error, data) {
// Convert strings to numbers.
data.forEach(function(d) {
d.people = +d.people
d.year = +d.year
d.age = +d.age
})
// Compute the extent of the data set in age and years.
var age1 = d3.max(data, function(d) { return d.age }),
year0 = d3.min(data, function(d) { return d.year }),
year1 = d3.max(data, function(d) { return d.year }),
year = year1
// Update the scale domains.
x.domain([year1 - age1, year1])
y.domain([0, d3.max(data, function(d) { return d.people })])
// Produce a map from year and birthyear to [male, female].
data = d3.nest()
.key(function(d) { return d.year })
.key(function(d) { return d.year - d.age })
.rollup(function(v) { return v.map(function(d) { return d.people }) })
.map(data)
// Add an axis to show the population values.
svg.append("g")
.attr("class", "y axis")
.attr("transform", "translate(" + width + ",0)")
.call(yAxis)
.selectAll("g")
.filter(function(value) { return !value })
.classed("zero", true)
// Add labeled rects for each birthyear (so that no enter or exit is required).
var birthyear = birthyears.selectAll(".birthyear")
.data(d3.range(year0 - age1, year1 + 1, 5))
.enter().append("g")
.attr("class", "birthyear")
.attr("transform", function(birthyear) { return "translate(" + x(birthyear) + ",0)" })
birthyear.selectAll("rect")
.data(function(birthyear) { return data[year][birthyear] || [0, 0] })
.enter().append("rect")
.attr("x", -barWidth / 2)
.attr("width", barWidth)
.attr("y", y)
.attr("height", function(value) { return height - y(value) })
// Add labels to show birthyear.
birthyear.append("text")
.attr("y", height - 4)
.text(function(birthyear) { return birthyear })
// Add labels to show age (separate not animated).
svg.selectAll(".age")
.data(d3.range(0, age1 + 1, 5))
.enter().append("text")
.attr("class", "age")
.attr("x", function(age) { return x(year - age) })
.attr("y", height + 4)
.attr("dy", ".71em")
.text(function(age) { return age })
// Allow the arrow keys to change the displayed year.
window.focus()
d3.select(window).on("keydown", function() {
switch (d3.event.keyCode) {
case 37: year = Math.max(year0, year - 10) break
case 39: year = Math.min(year1, year + 10) break
}
update()
})
function update() {
if (!(year in data)) return
title.text(year)
birthyears.transition()
.duration(750)
.attr("transform", "translate(" + (x(year1) - x(year)) + ",0)")
birthyear.selectAll("rect")
.data(function(birthyear) { return data[year][birthyear] || [0, 0] })
.transition()
.duration(750)
.attr("y", y)
.attr("height", function(value) { return height - y(value) })
}
})
