Creating map of Africa using d3.js and topoJSON

问题

i want to create map of Africa using d3.js and topoJSON. I have that datasource https://gist.githubusercontent.com/bricedev/3905007f1794b0cb0bcd/raw/ad5c995f6990f7c3c7fad5c6206bc6fd5462f1fb/africa.json

That is my code. How i can get properties and create correct map? Please help me where is the error?

<!DOCTYPE html>
<html>
<head>
<meta name="description" content="D3byEX 12.15" />
<meta charset="utf-8">
</head>
<body>
<script src="http://d3js.org/d3.v3.min.js"></script>
<script src="http://d3js.org/topojson.v1.min.js"></script>
    <script>
    var width = 1000, height = 728;


    var svg = d3.select("body").append("svg")
        .attr({ width: width, height: height });
    var mainGroup = svg.append("g");
    mainGroup.style({ stroke: "white", "stroke-width": "2px", "stroke-opacity": 0.0 });

    var projection = d3.geo.mercator();

    var path = d3.geo.path().projection(projection);

    var url = 'https://gist.githubusercontent.com/bricedev/3905007f1794b0cb0bcd/raw/ad5c995f6990f7c3c7fad5c6206bc6fd5462f1fb/africa.json';
    d3.json(url, function (error, africa) {
        var countries = topojson.feature(africa, africa.objects.countries).features;
        var neighbors = topojson.neighbors(africa.objects.countries.geometries);

        var color = d3.scale.category20();
        mainGroup.selectAll("path", "countries")
            .data(countries)
            .enter().append("path")
            .attr("d", path)
            .style("fill", function (d, i) {
                return color(d.color = d3.max(neighbors[i],
                    function (n) { return countries[n].color; }) + 1 | 0);
            });

        mainGroup.selectAll("path")
            .on("mouseover", function () {
                console.log("mouseover");
                d3.select(this).style("stroke-opacity", 1.0);
            });
        mainGroup.selectAll("path")
            .on("mouseout", function () {
                d3.select(this).style("stroke-opacity", 0.0);
            });
    });

</script>

回答1:

Your topojson is not in WGS84, that is to say lat/long coordinate space or unprojected data. D3.projection() requires WGS84.

Your topojson is already projected in, what I assume is, the Africa Lambert Conformal Conic projection. You do not need to use a projection to display this in d3.js. In order to display this data without a projection you can define the projection of your geoPath as:

path = d3.geoPath().projection(null);

This is how the topojson was projected in the block in which that data came from.

If you need to scale or translate the projection, then d3.geoTransform can help you, see this block.

Alternatively, you can reproject your topojson so that it uses lat/long pairs and will properly project using d3.projection().

来源：https://stackoverflow.com/questions/41231963/creating-map-of-africa-using-d3-js-and-topojson

标签

javascript

d3.js

maps

topojson