D3 Examples - Multi-Series Line Chart

Multi-Series Line Chart

This line chart is constructed from a TSV file storing the daily average temperatures of New York, San Francisco and Austin over the last year. The chart employs conventional margins and a number of D3 features:

d3.tsv - load and parse data

d3.time.format - parse dates

d3.time.scale - x-position encoding

d3.scale.linear - y-position encoding

d3.scale.category10, a d3.scale.ordinal - color encoding

d3.extent, d3.min and d3.max - compute domains

d3.keys - compute column names

d3.svg.axis - display axes

d3.svg.line - display line shape

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<!DOCTYPE html>
<meta charset="utf-8">
<style>
​
.axis--x path {
  display: none;
}
​
.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}
​
</style>
<svg width="960" height="500"></svg>
<script src="//d3js.org/d3.v4.min.js"></script>
<script>
// will keep track of which city is being shown and full name of city
var cityMap = {};
​
var svg = d3.select("svg"),
    margin = {top: 20, right: 80, bottom: 30, left: 50},
    width = svg.attr("width") - margin.left - margin.right,
    height = svg.attr("height") - margin.top - margin.bottom,
    g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")");
​
var parseTime = d3.timeParse("%Y%m%d");
​
var x = d3.scaleTime().range([0, width]),
    y = d3.scaleLinear().range([height, 0]),
    z = d3.scaleOrdinal(d3.schemeCategory10);
​
var line = d3.line()
    .curve(d3.curveBasis)
    .x(function(d) { return x(d.date); })
    .y(function(d) { return y(d.temperature); });
​
var zoom = d3.zoom()
    .scaleExtent([1 / 4, 8])
    .translateExtent([[-width, -Infinity], [2 * width, Infinity]])
    .on("zoom", zoomed);
​
var zoomRect = svg.append("rect")
    .attr("width", width)
    .attr("height", height)
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")")
    .attr("fill", "none")
    .attr("pointer-events", "all")
    .call(zoom);
​
g.append("clipPath")
    .attr("id", "clip")
    .append("rect")
    .attr("width", width+margin.right)
    .attr("height", height+margin.top+margin.bottom)
    .call(zoom);
​
  var xAxis = d3.axisBottom(x);
  var xGroup = g.append("g");
  var yGroup = g.append("g");
  var yAxis = d3.axisLeft(y);
​
d3.tsv("data.tsv", type, function(error, data) {
  if (error) throw error;
​
  var cities = data.columns.slice(1).map(function(id) {
    return {
      id: id,
      values: data.map(function(d) {
        return {date: d.date, temperature: d[id]};
      })
    };
  });
​
  x.domain(d3.extent(data, function(d) { return d.date; }));
  var xExtent = (d3.extent(data, function(d) { return d.date; }));
  zoom.translateExtent([[x(xExtent[0]), -Infinity], [x(xExtent[1]), Infinity]])
​
  y.domain([
    d3.min(cities, function(c) { return d3.min(c.values, function(d) { return d.temperature; }); }),
    d3.max(cities, function(c) { return d3.max(c.values, function(d) { return d.temperature; }); })
  ]);
​
  z.domain(cities.map(function(c) { return c.id }));
​
  // add all cities to shown map
  var allCities = (cities.map(function(c) { return c.id; }));
  for (index in allCities){
    cityMap[allCities[index].substring(0, 3).toUpperCase()] = {"shown": true, "full": allCities[index]};
  }
​
    xGroup.attr("class", "axis axis--x")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);
​
  yGroup.append("g")
      .attr("class", "axis axis--y")
      .call(yAxis)
      .append("text")
      .attr("transform", "rotate(-90)")
      .attr("y", 6)
      .attr("dy", "0.71em")
      .attr("fill", "#000")
      .text("Temperature, ºF");
​
    var city = g.selectAll(".city")
    .data(cities)
    .enter().append("g")
    .attr("clip-path", "url(#clip)")
    .attr("class", "city");
​
  city.append("path")
      .attr("class", "line")
      .attr("id", function(d){
          return d.id.substring(0, 3).toUpperCase();
      })
      .attr("d", function(d) { return line(d.values); })
      .style("stroke", function(d) { return z(d.id); });
​
  city.append("text")
      .datum(function(d) { return {id: d.id, value: d.values[d.values.length - 1]}; })
      .attr("transform", function(d) { return "translate(" + x(d.value.date) + "," + y(d.value.temperature) + ")"; })
      .attr("x", 3)
      .attr("dy", "0.35em")
      .attr("id", function(d){
        return d.id.substring(0, 3).toUpperCase();
      })
      .style("font", "10px sans-serif")
      .text(function(d) { return d.id; })
      .on("mouseover", function(d){
        var thisId = d.id.substring(0, 3).toUpperCase();
        if (cityMap[thisId].shown){
          for (city in cityMap){
            if (city != thisId){
              if (cityMap[city].shown){
                d3.select("path#" + city).style("stroke", "lightgray");
              }
            }
          } 
        }
      })
      .on("mouseout", function(d){
        for (city in cityMap){
          if (cityMap[city]){
            d3.select("path#" + city).style("stroke", z(cityMap[city].full));
          }
        } 
      })
      .on("click", function(d){
        var id = d.id.substring(0, 3).toUpperCase();
        var newOpacity = 0;
        newOpacity = cityMap[id].shown ? 0: 1;
        cityMap[id].shown = !(cityMap[id].shown);
        d3.select("path#" + id).style("opacity", newOpacity);
      });
​
      zoomRect.call(zoom.transform, d3.zoomIdentity);
});
​
function zoomed() {
      var xz = d3.event.transform.rescaleX(x);
      xGroup.call(xAxis.scale(xz));
​
      line.x(function(d) { return xz(d.date); })
      g.selectAll(".line")
        .attr("d", function(d) { return line(d.values); }); 
  }
​
​
function type(d, _, columns) {
  d.date = parseTime(d.date);
  for (var i = 1, n = columns.length, c; i < n; ++i) d[c = columns[i]] = +d[c];
  return d;
}
​
</script>
​
    