Alan Garcia adg29

Smooth transitioning US tour in the same vein as this example. Steps:

Compares both shapes and adds evenly-spaced points to whichever polygon has fewer so that both have the same number of points
Picks the winding of the first polygon that minimizes the sum of the squared distances between point pairs

Some possible improvements:

Adding additional points to both shapes first such that every segment longer than a certain distance is bisected
Tweaking the placement of added points with simulated annealing
Using a cost function that factors in self-intersections at the halfway mark in addition to distance traveled

Playing with reusing d3.geo for plotting. Subsequent example: http://bl.ocks.org/monfera/11085004

Mike Bostock and Jason Davies have added cool geo features, some of which can be of interest for regular data plotting too (most of which not covered in this example):

The use of projections to easily change between Cartesian, polar, spiral, etc. plots

d3.geo supports spherical projections; this example projects a sphere-bound spiral

Traditional, but data-intensive plots can benefit from adaptive resampling and line simplification

Demo of a bug that happens when you trigger updateChoropleth from a geography click. Fill is updated properly, but per the mouseout functions found at https://github.com/markmarkoh/datamaps/blob/master/src/js/datamaps.js#L523 & https://github.com/markmarkoh/datamaps/blob/master/src/js/datamaps.js#L252, when you mouseout from the just-selected geography, the fill reverts.

This is a demonstration of how to create a combination town/county map from a shapefile using TopoJSON and d3.js.

It includes a simplified version of the code used for the Massachusetts special Senate election results on The Huffington Post.

Get the data

Download a shapefile of Massachusetts towns from the state's GIS site:

wget http://wsgw.mass.gov/data/gispub/shape/census2000/towns/census2000towns_poly.exe

Some of these files are from the us-atlas:

us.json - make topo/us-10m.json
us-congress-113.json - make topo/us-congress-10m.json

Others are from the world-atlas:

world-50m.json - make topo/world-50m.json
world-110m.json - make topo/world-110m.json

US State Emissions Choropleth

A demo of TopoJSON on a U.S. counties shapefile from the U.S. census bureau. The same TopoJSON file can also be used to show states.

	import React from 'react';

	const ConditionalWrap = ({condition, wrap, children}) => condition ? wrap(children) : children;

	const Header = ({shouldLinkToHome}) => (
	<div>
	<ConditionalWrap
	condition={shouldLinkToHome}
	wrap={children => <a href="/">{children}</a>}
	>

	<!DOCTYPE html>
	<html lang="en">
	<head>
	<title>d3 geo map</title>
	<meta charset="utf-8">

	<style>
	svg {
	border: 1px solid #ccc;
	}

	(function() {

	var π = Math.PI,
	degrees = 180 / π,
	radians = π / 180,
	ε = 1e-15,
	circle = d3.geo.circle().angle(90);

	d3.geo.voronoi = function(points, triangles) {
	if (arguments.length < 2) triangles = d3.geo.delaunay(points);