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D3.js geoConicEqualArea() Function
  • Last Updated : 23 Sep, 2020

The geoConicEqualArea() function in d3.js is used to draw the Albers’ Conic equal-area projection from the given geojson data.

Syntax:

d3.geoConicEqualArea()

Parameters: This method does not accept any parameters.

Return Value: This method returns the Conic equal-area projection.

Example 1: The following example draws the Conic equal-area projection of the world with the center at (0, 0) and a rotation of 0 degrees.



HTML




<!DOCTYPE html>
<html>
  
<head>
    <script src="https://d3js.org/d3.v4.js">
    </script>
    <script src=
    </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");
  
        // ConicEqualArea projection with
        // Center at (0, 0) with rotation
        // of 0 degrees 
        var gfg = d3.geoConicEqualArea()
            .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 Conic equal-area projection of the world with the center at (-10, 0) and a 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=
    </script>
</head>
  
<body>
    <div style="width:700px; height:600px;">
        <svg width="500" height="450"></svg>
    </div>
      
    <script>
        var svg = d3.select("svg"),
            width = +svg.attr("width"),
            height = +svg.attr("height");
  
        // ConicEqualArea  projection
        // Center at (-10,0) and 90 degree
        // rotation w.r.t y-axis
        var gfg = d3.geoConicEqualArea()
            .scale(width / 1.8 / Math.PI)
            .rotate([90, 0])
            .center([-10, 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:

full-stack-img

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