Experimenting with grid histograms

11 Mar 2019 08:38 GMT

A few months ago, when ONS published their population estimates for Parliamentary constituencies in mid-2017, I worked on an analysis of constituencies by median age. This included some interacive charts produced with D3, which I was never able to publish as the online part of the project didn't get off the ground. Rather than see that work go to waste, I decided to publish the charts here for posterity.

The charts in question are grid histograms, which show the distribution of Parliamentary constituencies by median age at the 2017 General Election. In these charts, each square represents a single constituency, and each chart shows the squares shaded by another variable: such as party, turnout and majority. Click on the image below or the link above to see the interactive versions of these charts.

A set of four charts each showing the distribution of constituencies by median age and their relationship with another variable

On average, median age was lower in seats won by Labour and higher in seats won by the Conservatives. Turnout tended to be higher in seats with a higher median age. And some of Labour's biggest majorities were in seats with the lowest median age.

As a way of showing the strength of the relationship between two variables, I think this type of chart is probably less succesful than a scatterplot. But as a way of showing the distribution of one variable within another, I think it works quite well. Although perhaps better for the continuous variables than the categorical variable.