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D3.js – Axis API

D3.js - Axis API

In this D3.js Axis API chapter, D3 provides functions to draw axes. An axis is made of Lines, Ticks and Labels. An axis uses a Scale, so each axis will need to be given a scale to work with.

Configuring the Axis API

You can configure the API using the following script.

<script src = "https://d3js.org/d3-axis.v1.min.js"></script>
<script>

</script>

Axis API Methods

D3 provides the following significant functions to draw axes. They are described in brief as follows.

  • d3.axisTop() − This method is used to create a top horizontal axis.
  • d3.axisRight() − This method is used to create a vertical right-oriented axis.
  • d3.axisBottom() − This method is used to create a bottom horizontal axis.
  • d3.axisLeft() − It creates left vertical axis.

Working Example

Let us learn how to add the x and y-axis to a graph. To do this, we need to adhere to the steps given below.

Step 1 − Define variables − Define SVG and data variables using the code below.

var width = 400, height = 400;
var data = [100, 150, 200, 250, 280, 300];
var svg = d3.select("body")
   .append("svg")
   .attr("width", width)
   .attr("height", height);

Step 2 − Create a scale linear function − Create a scale linear function for both x and y axis as defined below.

var xscale = d3.scaleLinear()
   .domain([0, d3.max(data)])
   .range([0, width - 100]);

var yscale = d3.scaleLinear()
   .domain([0, d3.max(data)])
   .range([height/2, 0]);

Here, we have created a linear scale and specified the domain and the range.

Step 3 − Add scales to x-axis − Now, we can add scales to the x-axis using the following code.

var x_axis = d3.axisBottom()
   .scale(xscale);

Here, we use d3.axisBottom to create our x-axis and provide it with the scale, which is defined earlier.

Step 4 − Add scales to the y-axis − Use the following code to add scales to the y-axis.

var y_axis = d3.axisLeft()
   .scale(yscale);

Here, we use the d3.axisLeft to create our y-axis and provide it with the scale we defined above.

Step 5 − Apply transformation − You can append a group element and insert the x, y axis, which is defined below.

svg.append("g")
   .attr("transform", "translate(50, 10)")
   .call(y_axis);

Step 6 − Append group elements − Apply transition and group elements using the following code.

var xAxisTranslate = height/2 + 10;
svg.append("g")
   .attr("transform", "translate(50, " + xAxisTranslate  +")")
   .call(x_axis)

Step 7 − Working Example − The complete code listing is given in the following code block. Create a webpage axes.html and add the following changes to it.

<html>
   <head>
      <script type = "text/javascript" src = "https://d3js.org/d3.v4.min.js"></script>
      <style>
         svg text {
            fill: purple;
            font: 12px sans-serif;
            text-anchor: end;
         }
      </style>
   </head>

   <body>
      <script>
         var width = 400, height = 400;
         var data = [100, 120, 140, 160, 180, 200];
         var svg = d3.select("body")
            .append("svg")
            .attr("width", width)
            .attr("height", height);
         
         var xscale = d3.scaleLinear()
            .domain([0, d3.max(data)])
            .range([0, width - 100]);
         
         var yscale = d3.scaleLinear()
            .domain([0, d3.max(data)])
            .range([height/2, 0]);
    
         var x_axis = d3.axisBottom().scale(xscale);
         
         var y_axis = d3.axisLeft().scale(yscale);
         
         svg.append("g")
            .attr("transform", "translate(50, 10)")
            .call(y_axis);
         
         var xAxisTranslate = height/2 + 10;
         
         svg.append("g")
            .attr("transform", "translate(50, " + xAxisTranslate  +")")
            .call(x_axis)
      </script>
   </body>
</html>

Now, request the browser and we will see the following changes in D3.js Axis API.

D3.js - Axis API

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