Data Visualisation: Putting Voter Turnout on the Map

Posted by John Durance on 09 Apr, 2015

With a general election less than one month away the news will soon be filled with election predictions and statistics. Such election data is a perfect subject for a project I am currently working on. The aim of this project is to create a data visualisation tool that can display big datasets in innovative and interesting ways. These data visualisations will be easy to share and accessible to all users.

Presently, I am working on maps with areas coloured to represent a different value depending on where it falls on a scale. The technical term for this kind of data visualisation is a choropleth. There are some complex mathematics involved in generating a choropleth: automatically computing the scale from the uploaded data, projecting the spherical earth as a flat map etc. Fortunately, D3, which is at the core of the tool I am building, has functions to handle all of these tasks.

The map, below, is divided into Westminster parliamentary constituencies, which will be the battlegrounds for the parties hoping to win. The dataset used is the voter turnout for each of the constituencies during the last election. At a glance, it appears that less people turnout to vote in the cities and, generally, slightly more people in the south of England.

Data source: The Electoral Commission

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