d3-exploder

What is this?

This is a tiny d3 extension that lets you easily move and resize geographic features rendered with d3 and topojson.

Why would I want this?

Say you have a map of the US (like above) and you want to gratuitously transition the map into a scatter plot where the states are the points. This will let you do that. To see this in action, click the "scatter" button above.

How can I use this?

You can install via...

      npm install d3-exploder
    

And then import within javascript

      import { exploder } from 'd3-exploder';

var myExploder = exploder();
    

or include via a script tag

    <script src="http://d3js.org/d3.v4.min.js" charset="utf-8"></script>
<script src="http://d3js.org/topojson.v2.min.js"></script>
<script src="d3-exploder.min.js"></script>
  

Next, create a map with some geographic features... and then create an exploder function and call it!

    
var width = 960,
    height = 500;

var projection = d3.geoAlbersUsa().scale(width);

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

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

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


d3.json("us.json", function(error, us) {

  var state_features = topojson.feature(
    us, us.objects.states
  ).features;

  var states = g.append("g")
      .attr("id", "states")
    .selectAll("path")
      .data(state_features)
    .enter().append("path")
      .attr("d", path);


  // Here is the magic!
  // This exploder will create a grid of the states
  // when called on a featurelist selection
  var exploder = d3.exploder()
                  // use the same projection as the map
                  .projection(projection)
                  // provide a function to determine the size
                  // of each feature when called
                  .size(function(d, i) { return 40; })
                  // provide a function to determine the
                  // new (grid) positions of the features
                  // -> returns an [x, y] array (in pixels)
                  .position(function(d, i) {
                    var px = Math.max(0, width - 9*60)/2
                    return [px + (i%10)*60, 70 + Math.floor(i/10)*60];
                  })
  //
  // transition to the grid
  //
  states
    .transition()
    .duration(500)
    .call(exploder);

});