D3.js areaRadial.context() Method

Last Updated : 02 Sep, 2020

The areaRadial.context() method in D3.js lets you specify the canvas element’s context in which the area radial would be rendered. The area radial will be rendered in the current context when the generator is invoked. We can set the context of the area on our own using this method like color, stroke, fill, etc. The default value is null.

Syntax:

d3.areaRadial.context( _context )

Parameters: This method accepts a single parameter as mentioned above and described below:

_context: It is context set by the user.

Return Value: This method returns the current context.

Below given are a few examples of areaRadial.context() method in D3.js:

Example 1:

HTML

<!DOCTYPE html> 
<html> 
<head> 
  <script src= 
"https://d3js.org/d3.v5.min.js"> 
  </script> 
</head> 
<body> 
  <h1 style="text-align: center; 
             color: green;"> 
    GeeksforGeeks 
  </h1> 
  <h3 style="text-align: center;"> 
    D3.js | areaRadial.context() Method 
  </h3> 
  <center> 
    <canvas id="gfg" width="200" height="200"> 
    </canvas> 
  </center> 
  <script> 
    var points = [ 
      { x: 0, y: 0 }, 
      { x: 2, y: 3 }, 
      { x: 4, y: 1 }, 
      { x: 6, y: 8 }, 
      { x: 8, y: 17 }, 
      { x: 10, y: 15 }, 
      { x: 12, y: 20 }]; 
  
    // Get the context 
    var context = d3.select("#gfg") 
        .node() 
        .getContext("2d"); 
  
    var xScale = d3.scaleLinear() 
        .domain([0, 6]) 
        .range([0, 2 * Math.PI]); 
    var yScale = d3.scaleLinear() 
        .domain([0, 20]) 
        .range([90, 30]); 
  
    var Gen = d3.areaRadial() 
      .angle(d => xScale(d.x / 2)) 
      .innerRadius(d => yScale(d.y) / 2) 
      .outerRadius(d => yScale(d.y)) 
      
      // Specify the context 
      // to be used 
      .context(context); 
  
    context.translate(100, 100); 
    Gen(points); 
    context.strokeStyle = "black"; 
    context.fillStyle = "green"; 
    context.fill(); 
    context.stroke(); 
  </script> 
</body> 
</html>

Output:

Example 2:

HTML

<!DOCTYPE html> 
<html> 
<head> 
  <script src= 
"https://d3js.org/d3.v5.min.js"> 
  </script> 
</head> 
<body> 
  <h1 style="text-align: center; 
             color: green;"> 
    GeeksforGeeks 
  </h1> 
  <h3 style="text-align: center;"> 
    D3.js | areaRadial.context() Method 
  </h3> 
  <center> 
    <canvas id="gfg" width="200" height="200"> 
    </canvas> 
  </center> 
  <script> 
    var data = [ 
      { x: 10, y: 1 }, 
      { x: 15, y: 3 }, 
      { x: 20, y: 5 }, 
      { x: 25, y: 7 }, 
      { x: 30, y: 9 }, 
      { x: 35, y: 11 }, 
      { x: 40, y: 13 }]; 
  
    // Get the context 
    var context = d3.select("#gfg") 
        .node() 
        .getContext("2d"); 
  
    var xScale = d3.scaleLinear() 
        .domain([0, 6]) 
        .range([0, 2 * Math.PI]); 
    var yScale = d3.scaleLinear() 
        .domain([0, 20]) 
        .range([90, 30]); 
  
    var Gen = d3.areaRadial() 
      .angle(d => xScale(d.x / 2)) 
      .innerRadius(d => yScale(d.y) / 2) 
      .outerRadius(d => yScale(d.y)) 
  
      // Specify the context 
      // to be used 
      .context(context); 
  
    context.translate(100, 100); 
    Gen(data); 
    context.strokeStyle = "black"; 
    context.fillStyle = "green"; 
    context.fill(); 
    context.stroke(); 
  </script> 
</body> 
</html>