Thursday, July 28, 2016

Election Chartograms

The major winner in the last UK general election was the tiled grid map. My bet for this year's U.S. election is the 'chartogram'.

For example this week the Wall Street Journal has created an historical U.S. election map which represents each state as a bar chart showing the state winners in previous elections. A Field Guide to Red and Blue America is similar to a traditional tiled grid map, except dynamic bar charts have been used instead of colored grids. At the risk of butchering the English language I'm going to refer to this type of grid map as a 'chartogram'.

This isn't the first time that individual grids have been used to visualize historical election data. For example, after the Scottish Election in May, The Guardian used Sankey diagrams in a tiled grid map of Scotland to show the historical percentage of votes by each political party over previous elections in each electoral district.

Esri has also been experimenting with using different types of charts and graphs within individual tiled map grids to visualize U.S. election history data. US Election History is an interactive tiled grid map which visualizes the historical voting pattern of each state in a number of different ways.

My favorite view in this tiled grid map is the Waffle Grid, which presents the historical election data in each state with a series of small colored squares. Each square is colored red or blue to show how the state voted in previous US elections.

The Wall Street Journal is showing similar historical election data, only it is using bar charts rather than 'waffle grids'.

I have a feeling that we might be seeing quite a few of these types of tiled grid maps or chartograms in the next six months. If you want to create an interactive version of this type of map then it might be a good idea to start honing your d3.js skills and practice adding an SVG overlay pane to Leaflet maps.

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