I was immediately struck by how user-friendly it is – once I had watched the ‘how it works’ tutorial video, I felt like I knew what I was doing.
I wanted to create a map showing earthquakes that have hit Japan. At this point, I was viewing other people’s visualisations and I noticed one of the sources was ‘The International Disaster Database.’ I thought this would be a good place to start looking for data on Japan’s seismic activity.
I carried out a Country Profile Search on the website and it came up with a dataset of earthquakes in Japan (“EM-DAT: The OFDA/CRED International Disaster Database – www.emdat.net – Université catholique de Louvain – Brussels – Belgium.”)
Once the data was downloaded on my Google spreadsheet, I decided to focus on earthquakes of over 6.5 on the Richter scale to have hit Japan since 1703. I also selected the variables I wanted to use in my visualisation: place name, magnitude and date.
When you first open a new Workbook on Tableau Public, you have to ‘connect’ it to your data.
It takes a few seconds to transfer and then all your variables appear on the side. You can drag and drop them into the ‘rows’, ‘columns’ or ‘marks’ section and then select the type of visualiation you want.
This is where I struggled. Tableau Public did not recognise the place names in my data, maybe because some of them were the names of towns and others were provinces or islands. Had I known Japan well, I might have been able to change all the place names to the nearest town names.
In the end, I added two variables to my dataset: longitude and latitude. At first I added them in this form: ’33°00’N; 142°00’E’. This didn’t work.
So I simply kept the number, without even the North, South, East, West mark-ups. For example, for the Tokyo 1703 earthquake, the longitude column read ‘139’ and the latitude column read ’35.’
Much to my surprise, once I’d connected my new dataset, a multitude or circular markers appeared over Japan.
Once this is sorted, you can start personalising your work, by changing the colours and size of the markers and experimenting with different visualisations. I was able to select and de-select variables to change the focus of my research.
As well as the map, I made a bar diagram showing the severity of earthquakes over the centuries.
What makes Tableau Public such a fantastic journalistic tool is its flexibility – it allows you to look at different angles of one story using the same visualisation. And, once you’re past the headache of place names, it’s strangely addictive…
Claire Gilmore (@ClaireEGilmore)