Rolling Choropleth Globe in D3

Programmable rolling chloropeth globe in D3 with modifiable country colors, tool-tips and rotations. Pre-compiled to be dropped into your webpage.

Demo: https://boscoh.github.io/rolling-globe

Installation

Download the package.

Open the file example/index.html in the browser.

How-to

Quick-start. To create a globe, you need require.js and rolling-globe.min.js from the dist directory in the package. Then in your HTML file:

<div 
  id="globe"
  style="
    width: calc(100vw - 60px);
    height: calc(100vh - 160px);">
</div>

<script src="./require.js"></script>

<script>
require(['./rolling-globe.min.js'], function (rollingGlobe) {
    var g = new rollingGlobe.Globe('#globe')
})
</script>

Matching country indices. To access the the countries in the globe, you need to obtain the index of the country. This can be obtained using the getICountry method, with a query based on the built-in country properties (described in the section Looking up Countries below). To find Australia:

var i = g.getICountry({'iso_a3': 'AUS'})

Rotation to a selected country.

g.rotateTransitionToICountry(i)

Handle clicks and double-clicks.

g.clickCountry = function (i) {
  console.log('clicked: ' + g.features[i].properties.name)
  g.setHighlight(i)
  g.rotateTransitionToICountry(i, function () {
    g.draw()
  })
}

Setting country colors.

g.colors[i] = 'green'
g.borderColors[i] = 'blue'

Setting color palette based on country values.

// let's say populations is a list of country
// populations sorted by the country index
for (var i = 0; i < g.values.length; i += 1) {
  g.values[i] = populations[i]
}
g.resetCountryColorsFromValues('red')
g.draw()

// optional legend
g.drawLegend()

Highlight specific countries with outline.

g.highlightColor = 'green'
g.iHighlightCountry = i
g.draw()

Replace tool-tip.

g.getCountryPopupHtml = function (i) {
  return g.features[i].properties.name + ': ' + g.values[i]
}

Resize: The resize method will resize the globe to fit the parent <div>. Attach the function the window resize function:

window.onresize = function() { g.resize() }

Development

Download package and load the module using require.js

The module has been written in ES6, a very nice dialect, and transpiled into a single file for easy deployment, which includes all the necessary data files to get up and running. To compile dist/globe.min.js use:

> npm intall
> webpack

During development, it is suggested to run with the file watcher, and re-load example/index.html which uses the compiled version in the dist directory:

> webpack --watch

Looking up Countries

Each country is internally represented by an index iCountry, which refers to SVG vector data stored in this.world. This index is used to access the this.values, this.colors, this.borderColors and this.features.

Each country comes with a default set properties, which is stored in a list this.features. Each element in this list feature has a sub-field dictionary feature.properties, such as this one for Australia:

{
  "scalerank": 1,
  "featurecla": "Admin-0 country",
  "labelrank": 2,
  "sovereignt": "Australia",
  "sov_a3": "AU1",
  "adm0_dif": 1,
  "level": 2,
  "type": "Country",
  "admin": "Australia",
  "adm0_a3": "AUS",
  "geou_dif": 0,
  "geounit": "Australia",
  "gu_a3": "AUS",
  "su_dif": 0,
  "subunit": "Australia",
  "su_a3": "AUS",
  "brk_diff": 0,
  "name": "Australia",
  "name_long": "Australia",
  "brk_a3": "AUS",
  "brk_name": "Australia",
  "brk_group": "",
  "abbrev": "Auz.",
  "postal": "AU",
  "formal_en": "Commonwealth of Australia",
  "formal_fr": "",
  "note_adm0": "",
  "note_brk": "",
  "name_sort": "Australia",
  "name_alt": "",
  "mapcolor7": 1,
  "mapcolor8": 2,
  "mapcolor9": 2,
  "mapcolor13": 7,
  "pop_est": 21262641,
  "gdp_md_est": 800200,
  "pop_year":` -99,
  "lastcensus": 2006,
  "gdp_year":` -99,
  "economy": "2. Developed region: nonG7",
  "income_grp": "1. High income: OECD",
  "wikipedia":` -99,
  "fips_10": "",
  "iso_a2": "AU",
  "iso_a3": "AUS",
  "iso_n3": "036",
  "un_a3": 36,
  "wb_a2": "AU",
  "wb_a3": "AUS",
  "woe_id":` -99,
  "adm0_a3_is": "AUS",
  "adm0_a3_us": "AUS",
  "adm0_a3_un":` -99,
  "adm0_a3_wb":` -99,
  "continent": "Oceania",
  "region_un": "Oceania",
  "subregion": "Australia and New Zealand",
  "region_wb": "East Asia & Pacific",
  "name_len": 9,
  "long_len": 9,
  "abbrev_len": 4,
  "tiny":` -99,
  "homepart": 1
}

To lookup the iCountry index:

• you can iterate through the country features this.features and match the properties of each country to your country identifier.
• or use a default dictionary this.iCountryFromId that maps the iCountry index to iso_n3 field of a country feature.
• use the lookup method this.getICountry({key: value}), which will match the key, value pair to the values in feature.properties of each country, and return the iCountry index if successful

References

The SVG vector data is stored in this.world, and this is taken from Mike Bostocks's world-atlas, which was generated from the data at Natural Earth at the resolution of 1:110.

The Globe object has the following properties:

• this.world - topoJson data used to generate the SVG
• this.features - list of features for each country
• this.values - list of numerical values for each country
• this.colors - list of colors for countries
• this.borderColors - list of colors for borders of countries
• this.iCountryFromId - dictionary to map iso_n3 to iCountry indice
• this.nullColor - color of country with values set to null
• this.borderColor - color of country borders
• this.outerBorderColor - color of globe border
• this.fillColor - color of water
• this.highlightColor - color of border outline for highlighted country
• this.scaleFactor - zoom factor for globe
• this.iHighlightCountry - iCountry to be highlighted with this.highlightColor; none if null

Methods:

• this.getICountry(query) - query comes in the form of {key: value} that is used to search this.features for a matching property, function will return matchin iCountry index, or null
• this.dblclickCountry(iCountry) - overridable callback for double-click
• this.clickCountry(iCountry) - overridable callback fro click
• this.getCountryPopupHtml(iCountry) - overridable callback to generate the HTML for the tool-tip pop-up for a country mouse-over.
• this.resize() - resizes the globe to the size of the parent div. Useful for web-responsive divs.
• this.rotateTo(r) - direct rotation to the rotational coordinate r=[-Longitude, -Latitude], this is the internal D3 rotational coordinate system.
• this.rotateTransition(targetR, callback) - animated transition analogue to this.rotateTo with callback upon end of animation
• this.rotateTransitionToICountry(iCountry, callback) - animated rotation to country
• this.resetCountryColorsFromValues(maxColor, maxValue = null, minColor = '#DDD') - recolors the countries using this.values from maxColor to minColor using a linear color palette
• this.draw() - force redraw