D3.js geoWiechel() Function

Last Updated : 23 Sep, 2020

D3.js is a JavaScript library for producing dynamic, interactive data visualizations in web browsers. It makes use of Scalable Vector Graphics, HTML5, and Cascading Style Sheets standards.

The geoWiechel() function in d3.js is used to draw The Wiechel projection which is an azimuthal, equal-area projection, and a novelty map presented by William H. Wiechel in 1879. It is also a modified azimuthal projection. Distortion of direction, shape, and distance is considerable in the edges.

Syntax:

d3.geoWiechel()

Parameters: This method does not accept any parameters.

Return Value: This method creates and returns Wiechel projection from given JSON data.

Example 1: The following example makes the Wiechel projection of the world with the center at (0,0) and 0 rotation.

HTML

<!DOCTYPE html>  
<html lang="en">  
  
<head>  
    <meta charset="UTF-8" />  
    <meta name="viewport"
        content="width=device-width,  
                initial-scale=1.0"/>  
  
    <script src="https://d3js.org/d3.v4.js"></script> 
  
    <script src= 
"https://d3js.org/d3-geo-projection.v2.min.js"> 
    </script> 
</head>  
  
<body>  
    <div style="width:700px; height:500px;">  
        <svg width="600" height="450">  
        </svg>  
    </div>  
      
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Wiechel projection 
        // Center(0,0) with 0 rotation 
        var gfg = d3.geoWiechel() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([0,0]) 
            .center([0,0]) 
            .translate([width / 2, height / 2]); 
  
        // Loading the JSON data 
        d3.json("https://raw.githubusercontent.com/" 
            +"janasayantan/datageojson/master/world.json",  
            function(data){ 
                // Draw the map 
                svg.append("g") 
                    .selectAll("path") 
                    .data(data.features) 
                    .enter().append("path") 
                    .attr("fill", "DarkSlateGrey") 
                    .attr("d", d3.geoPath() 
                        .projection(gfg) 
                    ) 
                    .style("stroke", "#ffff") 
        }); 
    </script> 
</body>  
  
</html>

Output :

Wiechel projection of World with no rotation and centered at (0,0)

Example 2: The following example makes Wiechel projection of the world after customizing the center and rotation.

HTML

<!DOCTYPE html>  
<html lang="en">  
  
<head>  
    <meta charset="UTF-8" />  
    <meta name="viewport"
        content="width=device-width,  
                initial-scale=1.0"/>  
  
    <script src="https://d3js.org/d3.v4.js"></script> 
  
    <script src= 
"https://d3js.org/d3-geo-projection.v2.min.js"> 
    </script> 
</head>  
  
<body>  
    <div style="width:500px; height:600px;">  
        <svg width="500" height="450">  
        </svg>  
    </div>  
      
    <script> 
  
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Wiechel  projection 
        // Center(0,0) and -90 degree 
        // rotation w.r.t X axis 
        var gfg = d3.geoWiechel() 
            .scale(width / 1.3 / Math.PI) 
            .rotate([0,-90]) 
            .center([0,0]) 
            .translate([width / 2, height / 2]) 
  
        // Loading the json data 
        d3.json("https://raw.githubusercontent.com/" 
            +"janasayantan/datageojson/master/world.json",  
            function(data){ 
                // Draw the map 
                svg.append("g") 
                    .selectAll("path") 
                    .data(data.features) 
                    .enter().append("path") 
                    .attr("fill", "DarkSlateBlue") 
                    .attr("d", d3.geoPath() 
                        .projection(gfg) 
                    ) 
                    .style("stroke", "#ffff") 
        }) 
    </script> 
</body>  
  
</html>