When and Why you use a Sankey
A Sankey diagram is a great visualization to show the flow from one category to another. Sankeys are a great visualisation diagram to show off but are not always the go to chart when trying to practically show off a data visualisation. Sankeys should best be reserved for when you want to specify and emphasise the mapping between two categories of data. You can even continue a Sankey from its usual two comparisons and move on to having several breakdowns after the second. This becomes a multilevel or funnel Sankey. These are great at showing the flow of the data and how one certain value can change categorically over a period. Sankeys are best at showing breakdowns like in the Superstore dataset. You can make a Sankey from categories to subcategories show the number of subcategories in the categories and the flow from one to the other.
Creating a Sankey
Sankey charts are not easy to make, especially in tableau where the functionality has to be built from scratch. It’s often discouraging when starting to make one to be overwhelmed by the amount of math seen in the creation. Do not fear however there are multiple paths where to take from here.
I highly recommend following this guide by Brandon Fitz-Gerald from The Data School UK on how to quickly make a Sankey. Its easy to follow and requires no understanding of the underlying functions of the Sankey creation.
Though lengthier if you want more understanding of how the Sankey is being built and understand how its working in Tableau. I recommend Ian Baldwin’s guide from the Information Lab UK.