D3.js geoCraig() Function

Last Updated : 23 Sep, 2020

The geoCraig() function in d3.js is used to draw the Craig retroazimuthal projection from the given geojson data.

Syntax:

d3.geoCraig()

Parameters: This method does not accept any parameters.

Return Value: This method returns the Craig projection.

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

HTML

<!DOCTYPE html> 
<html> 
  
<head> 
    <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;"> 
        <center> 
            <h3 style="color:black"></h3> 
        </center> 
        <svg width="600" height="450"> 
        </svg> 
    </div> 
      
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Craig projection 
        // Center at (0,0) with 0 degree rotation 
        var gfg = d3.geoCraig() 
            .scale(width / 1.8 / 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) { 
  
                // Drawing the map 
                svg.append("g") 
                    .selectAll("path") 
                    .data(data.features) 
                    .enter().append("path") 
                    .attr("fill", "Black") 
                    .attr("d", d3.geoPath() 
                        .projection(gfg) 
                    ) 
                    .style("stroke", "#ffff") 
            }); 
    </script> 
</body> 
  
</html> 

Output:

Example 2: The following example draws the Craig projection of the world with the center at (20, 20) and rotation of -90 degrees with respect to the y-axis.

HTML

<!DOCTYPE html> 
<html> 
  
<head> 
    <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"></h3> 
        </center> 
        <svg width="500" height="450"> 
        </svg> 
    </div> 
      
    <script> 
        var svg = d3.select("svg"), 
            width = +svg.attr("width"), 
            height = +svg.attr("height"); 
  
        // Craig  projection 
        // Center at (20, 20) and  
        // -90 degree rotation w.r.t y-axis 
        var gfg = d3.geoCraig() 
            .scale(width / 1.8 / Math.PI) 
            .rotate([-90, 0]) 
            .center([20, 20]) 
            .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> 