24 Apr 2014 22:38 GMT
When I started experimenting with using d3 to produce maps a few months ago, my first attempt was a simple map showing the percentage of the population that spoke Welsh in each area of Ynys Môn at the 2011 Census. Last week I was back in Wales visiting relatives, and they wanted to know what an equivalent map would look like showing the percentage of people that could speak Welsh across the whole of Wales.
As I had my computer with me I couldn't resist having a go at working something up. The following map was produced fairly quickly, so it isn't interactive or even rendered directly using d3, but I thought it was visually interesting enough to share.
As before, the map shows the percentage of the population recorded as speaking Welsh in each Census output area. These are the smallest areas for which Census data is reported, so they provide a detailed picture of the variation in Welsh language ability at this scale.
The map is shaded using a visually linear scale from white to black through red: an area where no-one could speak Welsh would be shaded white, while an area in which everybody could speak Welsh would be shaded black. I haven't attempted to label the meaning of the colours any further, as in this case the purpose is to show the relative difference between areas at a glance rather than to provide a tool for exploratory analysis.
The most striking feature of the map is the clear division between the East and West of the country. North West Wales is the most Welsh part of Wales, especially around the Menai Strait and the Llŷn Peninsula. While Pembrokeshire in the South is an exception to the general rule.