Tuesday, 13 July 2010

UK Postcode mapping in 5 minutes


I have read a number of posts lately detailing approaches for handling mapping postcode data in the UK, so I thought I would write another one.  I think this is the fastest way to achieve it.

To map postcodes in Tableau, you somehow need to get the postcode

converted to a latitude and longitude.  There are many ways to do this, but I think this has the least steps.

Follow these steps to map the OUTCODE (the left hand side of a post code) to a Lat/Long.  The assumption is that you already have a dataset which includes POST CODE

Minutes 1 and 2 – Add a csv file to your copy of Tableau desktop, this tells Tableau the Lat/Long of the outcodes

You’ll need a csv file of outcodes, so I have posted one here.  Copy this file and save it.

Add it to tableau LIKE THIS…  Choosing the csv file from your save location.



Minute 3 – Create a calculated field which grabs the outcode from the postcode.  The function for the calculated field is something like this:

left([Postcode], find([Postcode], " ")-1)

This finds the space in the postcode, and returns the left portion which is equivalent to the outcode in the csv file.



Minute 4 – Change the ‘geographic role’ of your calculated field to be outcode.  Outcode is now available as a geographic role because of the csv file added



Minute 5 – Now you should be able to plot the outcode against a measure.  Select the outcode field, select ‘number of records’ (for example) and show me should now offer you a map.  Hey pesto, postcode mapping!



Happy mapping.


1 comment:

  1. Absolute Genious!! Saved me a lot of time and effort. Thanks Tom