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>
​
body {
  font: 10px sans-serif;
}
​
.axis path,
.axis line {
  fill: none;
  stroke:  #a9a9a9;
  shape-rendering: crispEdges;
}
​
​
.axis text {
  fill : darkgrey;  
  }
  
.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}
 svg {
    background-color : whitesmoke;
  }
​
​
</style>
<body>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
​
var margin = {top: 20, right: 80, bottom: 30, left: 70},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;
​
var parseDate = d3.time.format("%Y%m%d").parse;
​
var x = d3.time.scale()
    .range([0, width]);
​
var y = d3.scale.linear()
    .range([height, 0]);
​
var color = d3.scale.category10();
​
var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom");
​
var yAxis = d3.svg.axis()
    .scale(y)
    .orient("right")
    .tickFormat(function(d){return d +"º"});
​
var line = d3.svg.line()
    .interpolate("linear")
    .x(function(d) { return x(d.date); })
    .y(function(d) { return y(d.temperature); });
​
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 + ")");
​
d3.tsv("data.tsv", function(error, data) {
  if (error) throw error;
​
  color.domain(d3.keys(data[0]).filter(function(key) { return key !== "date"; }));
​
  data.forEach(function(d) {
    d.date = parseDate(d.date);
  });
​
  var cities = color.domain().map(function(name) {
    return {
      name: name,
      values: data.map(function(d) {
        return {date: d.date, temperature: +d[name], name: name};
      })
    };
  });
​
  x.domain(d3.extent(data, function(d) { return d.date; }));
​
  y.domain([
    d3.min(cities, function(c) { return d3.min(c.values, function(v) { return v.temperature; }); }),
    d3.max(cities, function(c) { return d3.max(c.values, function(v) { return v.temperature; }); })
  ]);
    
  y.domain([y.domain()[0]-5, y.domain()[1]+5]);
  
  //x axis
  svg.append("g")
      .attr("class", "x axis")
      .attr("transform", "translate(0," + height + ")")
      .call(xAxis);
  
    //y axis
  svg.append("g")
      .attr("class", "y axis")
            .attr("transform", "translate(" + (width) + ",0)")
      .call(yAxis)
    .append("text")
     .attr("transform", "rotate(270)") 
      .attr("y", -15)
      .attr("dy", ".71em")
      .style("text-anchor", "end")
      .text("Temp (ºF)");
      
​
  var city = svg.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 color(d.name); });
  
  var point = city.append("g")
  .attr("class", "line-point");
​
  point.selectAll('dot')
  .data(function(d){ return d.values})
  .enter().append('circle')
  .attr("cx", function(d) { return x(d.date) })
  .attr("cy", function(d) { return y(d.temperature) })
  .attr("r", 1.5)
  .style("fill", function(d) {return color(d.name);})
  .style("stroke", function(d) { return color(this.parentNode.__data__.name); });
  
    var colors = function(d) {
    return color(d.name);
  }
  
  city.append("text")
      .datum(function(d) { return {name: d.name, value: d.values[0]}; })
      .attr("transform", function(d) { return "translate(" + x(d.value.date) + "," + y(d.value.temperature) + ")"; })
        .attr("x", function(d) {
            if (d.name === "San Francisco") {
                            return -65;
                    }
                    else if (d.name === "New York") {
                return -45;
            }
                    else {
                return -30;
            }
            })
        .attr("dy", function(d) {
            if (d.name === "San Francisco") {
                            return ".95em";
                    }
                    else {
              return ".35em";
            }
            })
        .attr("fill" , function(d) {return colors(d)})
        .text(function(d) {return d.name;});
  
});
​
</script>
​
    