dots on a map: setup

This is a simple setup of Leaflet (via Mapbox) with d3 to show dots on a map. This can serve as a base for many interesting geographically based visualizations

Nice overview of using d3 + Leaflet. I found this slightly simpler to use than Mike's classic post.

Built with blockbuilder.org

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <script src='https://api.mapbox.com/mapbox.js/v2.2.3/mapbox.js'></script>
  <link href='https://api.mapbox.com/mapbox.js/v2.2.3/mapbox.css' rel='stylesheet' />
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
    #map { 
      position:absolute; 
      width: 100%;
      height: 100%;
    }
  </style>
</head>

<body>
  <div id="map"></div>
  <script>
   
    L.mapbox.accessToken = 'pk.eyJ1IjoiZW5qYWxvdCIsImEiOiJjaWhtdmxhNTIwb25zdHBsejk0NGdhODJhIn0.2-F2hS_oTZenAWc0BMf_uw'
    
    //Setup our Leaflet map using Mapbox.js
    var map = L.mapbox.map('map', 'mapbox.pencil', {maxZoom: 18, minZoom: 14})
    .setView([51.5119112,-0.10000], 15);
    
    // Setup our svg layer that we can manipulate with d3
    var svg = d3.select(map.getPanes().overlayPane)
      .append("svg");
    var g = svg.append("g").attr("class", "leaflet-zoom-hide");
    
    function project(ll) {
      // our data came from csv, make it Leaflet friendly
      var a = [+ll.lat, +ll.lon]; 
      // convert it to pixel coordinates
      var point = map.latLngToLayerPoint(L.latLng(ll))
      return point;
    }
  
    d3.csv("dots.csv", function(err, data) {
      var dots = g.selectAll("circle.dot")
        .data(data)
      
      dots.enter().append("circle").classed("dot", true)
      .attr("r", 1)
      .style({
        fill: "#0082a3",
        "fill-opacity": 0.6,
        stroke: "#004d60",
        "stroke-width": 1
      })
      .transition().duration(1000)
      .attr("r", 6)
      
      
      function render() {
        // We need to reposition our SVG and our containing group when the map
        // repositions via zoom or pan
        // https://github.com/zetter/voronoi-maps/blob/master/lib/voronoi_map.js
        var bounds = map.getBounds();
        var topLeft = map.latLngToLayerPoint(bounds.getNorthWest())
        var bottomRight = map.latLngToLayerPoint(bounds.getSouthEast())
        svg.style("width", map.getSize().x + "px")
          .style("height", map.getSize().y + "px")
          .style("left", topLeft.x + "px")
          .style("top", topLeft.y + "px");
        g.attr("transform", "translate(" + -topLeft.x + "," + -topLeft.y + ")");

// We reproject our data with the updated projection from leaflet
        g.selectAll("circle.dot")
        .attr({
          cx: function(d) { return project(d).x},
          cy: function(d) { return project(d).y},
        })

}

// re-render our visualization whenever the view changes
      map.on("viewreset", function() {
        render()
      })
      map.on("move", function() {
        render()
      })

// render our initial visualization
      render()
    })
    
  </script>
</body>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js

https://api.mapbox.com/mapbox.js/v2.2.3/mapbox.js