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>
  
.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>
​
var svg = d3.select("svg"),
    margin = {top: 20, right: 50, bottom: 30, left: 80},
    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()
    .x(function(d) { return x(d.date); })
    .y(function(d) { return y(d.temperature); });
​
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]};
      })
    };
  });
  
  var minTemp = d3.min(cities, function(c) { return d3.min(c.values, function(d) { return d.temperature; }); });
  var maxTemp = d3.max(cities, function(c) { return d3.max(c.values, function(d) { return d.temperature; }); });
​
  x.domain(d3.extent(data, function(d) { return d.date; }));
​
  y.domain([minTemp - 5, maxTemp + 5]);
​
  z.domain(cities.map(function(c) { return c.id; }));
​
  g.append("g")
      .attr("class", "axis axis--x")
      .attr("transform", "translate(0," + height + ")")
      .call(d3.axisBottom(x));
​
  g.append("g")
      .attr("class", "axis axis--y")
        .attr("transform", "translate(" + (width) + ", 0)")
      .call(d3.axisRight(y).tickFormat(function(d) { return d + "º"; }))
    .append("text")
      .attr("transform", "rotate(90)")
      .attr("y", 6)
      .attr("dy", "0.71em")
      .attr("fill", "#000")
      .text("Fahrenheit");
​
  var city = g.selectAll(".city")
    .data(cities)
    .enter().append("g")
      .attr("class", "city");
​
  city.append("path")
      .attr("class", "line")
      .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[0]}; })
      .attr("transform", function(d) { return "translate(-3," + y(d.value.temperature) + ")"; })
      .attr("dy", function(d) {
            return (d.id === "San Francisco") ? "1em" : "0.35em";
      })
      .style("font", "10px sans-serif")
      .style("fill", function(d) { return z(d.id); })
        .style("text-anchor", "end")
      .text(function(d) { return d.id; });
​
  var marks = city.append("g")
        .selectAll("circle")
      .data(function(d) {
        return d.values;
      })
      .enter();
​
    marks.append("circle")
      .style("stroke", "white")
      .style("fill", function() {
        var city = d3.select(this.parentNode).datum().id;
            return z(city);
      })
        .attr("cx", function(d) {
         return x(d.date);
      })
        .attr("cy", function(d) {
        return y(d.temperature);
      })
        .attr("r", 2);
  
  var minMaxTempText = marks.filter(function(d) {
      if ((d.temperature === minTemp) || (d.temperature === maxTemp)) {
        return true;
      }
      return false;
    })
    .append("text")
    .attr("x", function(d) {
      return x(d.date);
    })
    .attr("y", function(d) {
      return y(d.temperature);
    })
    .attr("dy", function(d) {
      return (d.temperature === maxTemp) ? -5 : 15;
    })
    .style("text-anchor", "middle")
    .style("fill", function(d) {
      var city = d3.select(this.parentNode).datum().id;
        return z(city);
    })
    .text(function(d) {
      return d.temperature + "º";
    });
});
​
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>
​
    