Dynamically size points on D3 TopoJSON map

StackOverflow https://stackoverflow.com/questions/20958420

题

I have plotted points on a TopoJSON map using D3, with the following code:

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

<head>

<script src="js/d3.js"></script>
<script src="http://d3js.org/topojson.v0.min.js"></script>

<style>
path {
  stroke: white;
  stroke-width: 0.25px;
  fill: grey;
}
</style>

    </head>

<body>

<script>
var width = 960,
    height = 500;

var projection = d3.geo.mercator()


var svg = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);

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

var g = svg.append("g");

// load and display the World
d3.json("data/world-110m2.json", function(error, topology) {

// load and display the cities
d3.json("data/commodities3.json", function(error, data) {
    g.selectAll("circle")
       .data(data)
       .enter()
       .append("circle")
       .attr("cx", function(d) {
               return projection([d.location_lon, d.location_lat])[0];})
       .attr("cy", function(d) {
               return projection([d.location_lon, d.location_lat])[1];})
       .attr("r", 4)
       .style("fill", "green");







});

    //plot the path

g.selectAll("path")
      .data(topojson.object(topology, topology.objects.countries)
          .geometries)
    .enter()
      .append("path")
      .attr("d", path)
});

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

  });

svg.call(zoom)

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

I am now looking to size these points based on the value of d.commodity_text. Therefore if the commodity_text were to be equal to "Iron" for instance, the circle would be bigger? Thanks.

有帮助吗？

解决方案

You simply need to replace the static value for the radius with a function:

.attr("r", function(d) {
  if(d.commodity_text == "Iron") {
    return 6;
  } else {
    return 4;
  }
});
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