使用 D3 的 TopoJSON 渲染问题

Question

我使用 world-110m topojson 渲染了世界地图。我直接使用了 Jakob 在 D3 映射教程上提供的代码 - http://www.digital-geography.com/d3-js-mapping-tutorial-1-set-initial-webmap/#.V4iGN9J97IV

<!DOCTYPE html>
<meta charset="utf-8">

<!-- Set a style for our worldshape-data -->
  <style>
  path {
    stroke: red;
    stroke-width: 0.5px;
    fill: grey;
  }
  </style>
<body>

  <!-- implementation of the hosted D3- and TopoJson js-libraries -->
  <script src="http://d3js.org/d3.v3.min.js"></script>
  <script src="http://d3js.org/topojson.v0.min.js"></script>

  <!-- map creation --> 
  <script>
  // canvas resolution
  var width = 1000,
      height = 600;

  // projection-settings for mercator    
  var projection = d3.geo.mercator()
      // where to center the map in degrees
      .center([0, 50 ])
      // zoomlevel
      .scale(100)
      // map-rotation
      .rotate([0,0]);

  // defines "svg" as data type and "make canvas" command
  var svg = d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height);

  // defines "path" as return of geographic features
  var path = d3.geo.path()
      .projection(projection);

  // group the svg layers 
  var g = svg.append("g");

  // load data and display the map on the canvas with country geometries
  d3.json("world-110m.json", function(error, topology) {
      g.selectAll("path")
        .data(topojson.object(topology, topology.objects.countries)
            .geometries)
      .enter()
        .append("path")
        .attr("d", path)
  });

  // zoom and pan functionality
  /*var zoom = d3.behavior.zoom()
      .on("zoom",function() {
          g.attr("transform","translate("+ 
              d3.event.translate.join(",")+")scale("+d3.event.scale+")");
          g.selectAll("path")  
              .attr("d", path.projection(projection)); 
    });

  svg.call(zoom)*/

  </script>
</body>
</html>

现在我想重用这段代码来渲染印度地图。但是当我 link 它到印度 topoJSON 文件时，只创建了一个空白的 SVG。 js控制台报错- topojson.v0.min.js:1 Uncaught TypeError: Cannot read property 'type' of undefined

我已将 world-110m.json 和 india.json 放在 dropbox - https://www.dropbox.com/sh/wrxyngyq4jdie9c/AACG2-dTzC79rRvlxlOC5poBa?dl=0

Answer 1

这只是一个小错误。

topojson.object(topology, topology.objects.countries //wrong
topojson.object(topology, topology.objects.collection // right

下次检查数据，将其打印到控制台并检查其内容。

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