Subtracting streets from choropleths, and how it might help understand uncertainty

Two visualizations that have caught my eye recently both use the same idea of colouring in geographical blocks according to some aggregated statistic, but then removing the streets and uninhabited areas. This helps you navigate your way but also, suggests James Cheshire of Spatial.ly, might emphasise the fact that the data are aggregated and shouldn’t be assumed to be true at every sub-level of geography.

The first one is the rather beautiful LuminoCity:Image

This is the brainchild of Duncan Smith at City Geographics. It really brings home how clustered our workplaces are, which is a little silly in this day and age. The same idea was shown off by James Cheshire in a talk at the recent Royal Statistical Society conference, this time by his colleague Oliver O’Brien who has a blog called Suprageography. (Damn it, why are these geographers all so cool and connected while statisticians are, well…)

Image

There’s an almost irresistible urge with these zoomable maps to zoom in on your home, or place of work, or whatever. And this is where Cheshire reckons the advantage comes: when you see your own neighbourhood entirely coloured in the same, you realise that what you are seeing is aggregated area stats and not the absolute truth. That might just stop you from making any false interpretations of relationships by the ecological fallacy (what associations are true at aggregate level are not necessarily true at individual level, viz chocolate vs Nobel prizes). That idea is worth thinking about when drawing maps.

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