How do I build a map with a Bubble Overlay in Tableau?
As part of our Tableau Training at The Information Lab Ireland, we like to examine different charts and how best to use them to answer the questions of our data. Not everyone is a fan of bubble charts but they can have their place in Data Visualization when used correctly. Bubbles can quickly inform a viewer about relative concentration of data and using bubbles as an overlay on maps puts geographically-related data in context quickly for the viewer. With large data sets it gives the viewer a geographical overview of the data in question. In this instance we are again using a small data set that shows Minimum wages across 22 E.U. states.
The purpose of the viz is three fold. We want to show where there is a concentration of higher wages, we want to show country rank and we want to show the actual minimum wages (Gross Pay €) relative to each other. While a simple colour-coded, filled map would indeed show the rank and concentration of higher wages, the relative sizes of each bubble allows us to get a quick view of the relative differences in actual wages and invites us to inquire further.
How do I build a map with a bubble overlay in Tableau?
There’s not too much to the data this time round. This data was put together from data collected by Eurostat. It’s worth noting that there are some countries omitted, either because they don’t have a minimum wage or because data was not available at the time. For our purposes, it works perfectly and given that it is something that has been mentioned, most recently by President Macron, it is topical.
First things first, we need to get our map set up. It couldn’t be easier, simply pull your Country Dimension into the Marks card and use the dropdown menu to set it to Map.
So the first measure we want to put on our chart is the rank. In this case we have decided to show rank by colour ans we do this by again bringing our Measure SUM Rank into Colour on our Marks card. At this point many people would be happy to leave the viz like this and if it were the case that we simply wanted to show the rank, this would be entirely acceptable. Be we want to get a little bit more from our data and answer a few more questions.
The Relative Measures
Now by all means we could have used the rank measure again and used bubbles to illustrate the measure 1 – 22 but apart from making the bubbles really small, to the point of almost being invisible, it would also be a waste.
Remember we started this blog by pointing out that Bubble Charts as an overlay on a map were a great way of showing geographic concentration of data.
In this instance, we can see immediately that minimum wages in north east EU states are higher than the rest of the EU. We of course have seen this already on the previous filled (shaded) map but what the bubble lets you see is the relative gap between states and invites you to investigate the differences further. If for example we look at Slovenia and Germany, two countries that are, according to their colour, quite close in rank (6th and 9th), we can see that they are proportionately very far apart. Germany is almost twice the size of Slovenia and the figures bear that out… €1,498 versus €805.
Add a filter for better interactivity
As a final touch and to get the most out of the information we have, we can add a filter. This allows us to reset parameters and show geographic trends more clearly. In this case, we can see that there is quite a gulf between EU states in the north east and those around the Med and former Eastern Bloc.
Don’t forget to tidy your Tooltip
As always it’s a good idea to tidy your tooltip and do make sure to break it up where possible so that the information will be clearer on narrow devices such as phones.
The Information Lab (“TIL”) is a Gold resale partner of Tableau and Alteryx and offers related consulting and training across seven territories in Europe. TIL has offices in Ireland, the UK, Germany, France, Italy, the Netherlands and Luxembourg.
Clients include Coca-Cola, Close Bros Bank, PepsiCo, Deloitte, UBS, Solar Turbines & Boston Consulting Group. The Information Lab has worked with Close Brothers Bank to support their use of Alteryx for compliance with IFRS 9.
The Information Lab Ireland is at the forefront of creating a data-driven culture in Ireland. As part of its vision, The Information Lab Ireland regularly hosts free events throughout the country to show how being data-driven can improve decision making and lead to a better understanding of the world around us.
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