The Tableau viz below on flow data has been sitting on my computer unfinished for the last few months. It’s still not finished, it’s a bit rough, so don’t be analysing the patterns in too much detail. But it’s trying to show a different way of showing flow data. It needs some Zen master magic to make more of the idea.
I wanted to explore visualising flow patterns in Tableau as they are surprisingly difficult to show effectively due to occlusion of the data. While the resulting images of standard flow maps can can look great, it can be difficult to see any local patterns in the maps as long distances occlude shorter distances as seen in the image to the side.
To overcome this issue, the giCentre at City University use Origin Destination maps depicting flows as non-occluding cells, whilst still maintaining their geographical arrangement. They are essentially OD matrices with a 2D geographical ordering. See these links for more detailed information on the methodology.
For this viz, I’ve used the 2007 Commodity Flow Survey that produces data on the movement of goods within the United States to show the amount in millions of all commodities traded between states. The survey is the primary source of national and state-level data on domestic freight shipments by American establishments in mining, manufacturing, wholesale, auxiliaries, and selected retail industries.
The origin destination map of the US below, shows a set of small square multiples that represent the flow destination by state. These are then arranged together by each state, roughly in there geographical position in the US, which then represents the flow origin. It allows us to see all the patterns within states across the US far more easily in one view. For example the patterns in the mid-west states are easy to see, rather than being obscured by the coast to coast flows. The top map allows you to filter, and so focus, on the flows from just one state.