Most basic connected scatter plot




This post describes how to build a very basic connected scatter plot with d3.js. Note that it is basically a line chart with data points represented as well. Learn more about the theory of connected scatter plot in data-to-viz.com.


Connected scatter section

Steps:

  • The Html part of the code just creates a div that will be modified by d3 later on.

  • The first part of the javascript code set a svg area. It specify the chart size and its margin. Read more.

  • Data show the evolution of bitcoin price. read more.

  • Line is drawn using a path, and using the d3.line utility.

  • Dots are added using circle, like for a basic scatterplot.
<!DOCTYPE html>
<meta charset="utf-8">

<!-- Load d3.js -->
<script src="https://d3js.org/d3.v4.js"></script>

<!-- Create a div where the graph will take place -->
<div id="my_dataviz"></div>


<script>
// set the dimensions and margins of the graph
var margin = {top: 10, right: 30, bottom: 30, left: 60},
    width = 460 - margin.left - margin.right,
    height = 400 - margin.top - margin.bottom;
// append the svg object to the body of the page
var svg = d3.select("#my_dataviz")
  .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 + ")");
//Read the data
d3.csv("https://raw.githubusercontent.com/holtzy/D3-graph-gallery/master/DATA/connectedscatter.csv",
  // When reading the csv, I must format variables:
  function(d){
    return { date : d3.timeParse("%Y-%m-%d")(d.date), value : d.value }
  },
  // Now I can use this dataset:
  function(data) {
    // Add X axis --> it is a date format
    var x = d3.scaleTime()
      .domain(d3.extent(data, function(d) { return d.date; }))
      .range([ 0, width ]);
    svg.append("g")
      .attr("transform", "translate(0," + height + ")")
      .call(d3.axisBottom(x));
    // Add Y axis
    var y = d3.scaleLinear()
      .domain( [8000, 9200])
      .range([ height, 0 ]);
    svg.append("g")
      .call(d3.axisLeft(y));
    // Add the line
    svg.append("path")
      .datum(data)
      .attr("fill", "none")
      .attr("stroke", "#69b3a2")
      .attr("stroke-width", 1.5)
      .attr("d", d3.line()
        .x(function(d) { return x(d.date) })
        .y(function(d) { return y(d.value) })
        )
    // Add the points
    svg
      .append("g")
      .selectAll("dot")
      .data(data)
      .enter()
      .append("circle")
        .attr("cx", function(d) { return x(d.date) } )
        .attr("cy", function(d) { return y(d.value) } )
        .attr("r", 5)
        .attr("fill", "#69b3a2")
})
</script>

Related blocks →