D3 Examples - Age Distribution of Legislators Versus US Population

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<!DOCTYPE html>
<meta charset="utf-8">
<style>
​
body {
  font:18px 'Helvetica Neue';
}
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.bar {
  fill: steelblue;
}
​
.bar-pop {
  fill: #f484c2;
}
​
.axis text {
  font: 10px sans-serif;
}
​
.axis path, .axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}
​
</style>
<body>
<script src="https://d3js.org/d3.v3.min.js"></script>
<script>
​
var format = d3.time.format("%Y-%m-%d");
var yformat = d3.time.format("%Y");
​
d3.csv('ages.csv', function(err, popgender) {
d3.json('legislators.json', function(err, data) {
​
    var popo = {};
    popgender.forEach(function(p) {
        if (popo[p.age] === undefined) popo[p.age] = 0;
        popo[p.age] += +p.people;
    });
    var pop = d3.entries(popo).map(function(p) {
        return {
            key: p.key,
            people: +p.value
        };
    }).filter(function(p) {
    return p.key > 0;
    });
​
    var nowy = (new Date()).getFullYear();
    var ages = data.response.legislators.map(function(d) {
        return nowy - format.parse(d.legislator.birthdate).getFullYear();
    });
​
    var data = d3.nest()
        .key(function(d) {
            return Math.floor(d / 5) * 5;
        })
        .entries(ages);
​
    var margin = {top: 20, right: 20, bottom: 30, left: 40},
        width = 960 - margin.left - margin.right,
        height = 500 - margin.top - margin.bottom;
​
    var x = d3.scale.linear()
        .range([0, width]);
​
    var y = d3.scale.linear()
        .range([height, 0]);
​
    var ypop = d3.scale.linear()
        .range([height, 0])
        .domain([0, d3.max(pop, function(d) { return d.people })]);
​
    var xAxis = d3.svg.axis()
        .scale(x)
        .orient("bottom");
​
    var yAxis = d3.svg.axis()
        .scale(y)
        .orient("left");
​
    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 + ")");
​
    svg.append('g')
        .attr('transform', 'translate(750, 10)')
        .append('text').attr('class', 'bar')
        .text('legislators');
​
    svg.append('g')
        .attr('transform', 'translate(750, 40)')
        .append('text').attr('class', 'bar-pop')
        .text('us population');
​
    x.domain(d3.extent(data, function(d) { return d.key; }));
    y.domain(d3.extent(data, function(d) { return d.values.length }));
​
    svg.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);
​
    svg.append("g")
        .attr("class", "y axis")
        .call(yAxis)
      .append("text")
        .attr("transform", "rotate(-90)")
        .attr("y", 6)
        .attr("dy", ".71em")
        .style("text-anchor", "end")
        .text("Frequency");
​
    svg.selectAll(".bar")
        .data(data)
      .enter().append("rect")
        .attr("class", "bar")
        .attr("x", function(d) { return x(d.key - 5); })
        .attr("width", 20)
        .attr("y", function(d) { return y(d.values.length); })
        .attr("height", function(d) { return height - y(d.values.length); });
​
    svg.selectAll(".bar-pop")
        .data(pop)
      .enter().append("rect")
        .attr("class", "bar-pop")
        .attr("x", function(d) { return x(d.key - 5) + 22; })
        .attr("width", 20)
        .attr("y", function(d) { return ypop(d.people); })
        .attr("height", function(d) { return height - ypop(d.people); });
});
});
</script>
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