D3.js geoEckert4() 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 geoEckert4() function in d3.js is used to draw the Eckert IV projection which is an equal-area pseudocylindrical map projection. The length of the polar lines is half that of the equator, and lines of longitude are semi ellipses or portions of ellipses.

Syntax:

d3.geoEckert4()

Parameters: This method does not accept any parameters.

Return Value: This method creates an Eckert4 projection from given JSON data.

Example 1: The following example makes Eckert4 projection of the world with the center at (0,0) and no 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:600px;">  
        <svg width="700" height="550">  
        </svg>  
    </div>  
      
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // geoEckert Iv  projection 
        // Center(0,0) and no rotation 
        var gfg = d3.geoEckert4() 
            .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", "GREY") 
                   .attr("d", d3.geoPath() 
                       .projection(gfg) 
                    ).style("stroke", "#ffff") 
        }) 
    </script> 
</body>  
  
</html>

Output :

Eckert IV Projection with (0,0) center and 0 rotation

Example 2: The following example makes Eckert4 projection of the world with the center at (0,0) and 20-degree Rotation clockwise.

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:600px;">  
        <center>  
            <h3 style="color:black">  
            Eckert IV Projection of World 
            </h3>   
        </center> 
        <svg width="700" height="400">  
        </svg>  
    </div>  
      
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // geoEckert IV  projection 
        // Center(0,0) and rotating 20  
        // degree clockwise 
        var gfg = d3.geoEckert4() 
            .scale(width / 1.5 / Math.PI) 
            .rotate([20,0]) 
            .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", "GREY") 
                   .attr("d", d3.geoPath() 
                       .projection(gfg) 
                   ).style("stroke", "#ffff") 
        }) 
    </script> 
</body>  
  
</html>