Helmet Usage of DC Cyclists 2004-2012

Sourced from the 2012 DC Bicycle Count Summary, visualized with d3js.

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.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
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.browser text {
  text-anchor: end;
  fill:#fff;
  font-size:30px;
}

</style>
<body>
<script src="https://d3js.org/d3.v3.js"></script>
<script>

var margin = {top: 20, right: 20, bottom: 30, left: 50},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var parseDate = d3.time.format("%Y").parse,
    formatPercent = d3.format(".0%");

var x = d3.time.scale()
    .range([0, width]);

var y = d3.scale.linear()
    .range([height, 0]);

var color = d3.scale.category20();

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    .scale(x)
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    .tickFormat(formatPercent);

var area = d3.svg.area()
    .x(function(d) { return x(d.date); })
    .y0(function(d) { return y(d.y0); })
    .y1(function(d) { return y(d.y0 + d.y); });

var stack = d3.layout.stack()
    .values(function(d) { return d.values; });

var svg = d3.select("body").append("svg")
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    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

d3.csv("helmet.csv", function(error, data) {
  color.domain(['Helmet', 'No Helmet']);

data.forEach(function(d) {
    d.date = parseDate(d.year);
  });

var bikers = stack(color.domain().map(function(name) {
    return {
      name: name,
      values: data.map(function(d) {
        return {date: d.date, y: d[name] / 100};
      })
    };
  }));

x.domain(d3.extent(data, function(d) { return d.date; }));

var l = svg.selectAll(".browser")
      .data(bikers)
    .enter().append("g")
      .attr("class", "browser");

l.append("path")
      .attr("class", "area")
      .attr("d", function(d) { return area(d.values); })
      .style("fill", function(d) { return color(d.name); });

l.append("text")
      .datum(function(d) { return {name: d.name, value: d.values[d.values.length - 1]}; })
      .attr("transform", function(d) { return "translate(" + x(d.value.date) + "," + y(d.value.y0 + d.value.y / 2) + ")"; })
      .attr("x", -6)
      .attr("dy", ".35em")
      .text(function(d) { return d.name; });

svg.append("g")
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      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);

svg.append("g")
      .attr("class", "y axis")
      .call(yAxis);
});

</script>

Modified http://d3js.org/d3.v3.js to a secure url

https://d3js.org/d3.v3.js