Improved quadtree clustering in d3.carto.map allows for more seamless integration with hierarchical D3 layouts like Pack & Tree.
If you set the .cluster() property of a cartoLayer to true, it will cluster bsaed on a precomputed quadtree. Along with clustering, it appends "children" attributes of every point, which allows it to be passed to a hierarchical layout, as is done here with circle-packing.
A hierarchical infoviz layout like circle-packing shows the hierarchical structure of clustered cities, so that you can get a sense not only of the density of cities, but also the distribution.
Modified http://d3js.org/d3.v3.min.js to a secure url
Modified http://d3js.org/topojson.v1.min.js to a secure url
Modified http://d3js.org/d3.geo.projection.v0.min.js to a secure url
Updated missing url http://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/tile.js to /emeeks/f3105fda25ff785dc5ed/example/tile.js
Updated missing url http://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/d3.quadtiles.js to /emeeks/f3105fda25ff785dc5ed/example/d3.quadtiles.js
Updated missing url http://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/d3.geo.raster.js to /emeeks/f3105fda25ff785dc5ed/example/d3.geo.raster.js
Updated missing url https://rawgit.com/emeeks/d3-carto-map/master/d3.carto.map.js to https://cdn.jsdelivr.net/gh/emeeks/d3-carto-map/d3.carto.map.js
https://d3js.org/d3.v3.min.js
https://d3js.org/topojson.v1.min.js
https://d3js.org/d3.geo.projection.v0.min.js
https://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/tile.js
https://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/d3.quadtiles.js
https://bl.ocks.org/emeeks/raw/f3105fda25ff785dc5ed/d3.geo.raster.js
https://rawgit.com/emeeks/d3-carto-map/master/d3.carto.map.js