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D3.js geoLagrange() Function

  • Last Updated : 14 Oct, 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 geoLagrange() function in d3.js is used to draw the Lagrange conformal projection.

Syntax:

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d3.geoLagrange()

Parameters: This method does not accept any parameters.

Return Value: This method creates Lagrange conformal projection from given json data.



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




<!DOCTYPE html>
<html lang="en">
  
<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, 
                initial-scale=1.0" />
</head>
  
<body>
    <div style="width:700px; height:500px;">
        <center>
            <h3 style="color:black">
            </h3>
        </center>
        <svg width="600" height="450">
        </svg>
    </div>
    <script src="https://d3js.org/d3.v4.js"></script>
    </script>
    <script>
  
        var svg = d3.select("svg"),
            width = +svg.attr("width"),
            height = +svg.attr("height");
  
        // Lagrange projection
        // Center(0, 0) with 0 rotation
        var gfg = d3.geoLagrange()
            .scale(width / 1.8 / Math.PI)
            .rotate([0, 0])
            .center([0, 0])
            .translate([width / 2, height / 2])
  
        // Loading the json data
        // Used json file stored at
        /datageojson/master/world.json*/
        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>

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

Example 2: The following example draws Lagrange projection of world after altering the center and rotation.




<!DOCTYPE html>
<html lang="en">
  
<head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, 
                initial-scale=1.0" />
</head>
  
<body>
    <div style="width:700px; height:600px;">
        <center>
            <h3 style="color:black">
            </h3>
        </center>
        <svg width="500" height="450">
        </svg>
    </div>
    <script src="https://d3js.org/d3.v4.js"></script>
    <script src=
    </script>
    <script>
  
        var svg = d3.select("svg"),
            width = +svg.attr("width"),
            height = +svg.attr("height");
  
        // Lagrange projection
        // Center(0, 20) and 20 degree
        // rotation w.r.t Y axis
        var gfg = d3.geoLagrange()
            .scale(width / 1.5 / Math.PI)
            .rotate([20, 0])
            .center([0, 20])
            .translate([width / 2, height / 2])
  
        // Loading the json data
        // Used json file stored at
        /datageojson/master/world.json*/
        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", "Turquoise")
                    .attr("d", d3.geoPath()
                        .projection(gfg)
                    )
                    .style("stroke", "#ffff")
            })
    </script>
</body>
  
</html>

Output:

Lagrange projection with  20 degree rotation w.r.t  Y axis  and centered at (0, 20)




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