Can You Create Step Area Charts?
Aug 31, 2019Klaus Schulte
Some weeks ago, I was very honored to be a guest host for the week 32 WorkoutWednesday challenge. Thanks again to Ann, Lorna, Luke, and Curtis for having me! In this blog, you can now find the long overdue solution guide!
Step Line Charts have been introduced with Tableau’s 2018.1 release and it’s really hard to remember that there was a time before, where it needed a little hack to create such a step line.
For the Area mark, we haven’t got the same options to create Step Area Charts yet. During Ludovic Tavernier‘s and my talk at TCE in Berlin some weeks ago I demoed how to create them using one extra copy of the data, and I also described the how-to in a blog earlier this year.
After my presentation in Berlin, I talked to Ann Jackson about my Step Area Chart and she was wondering (I assume she was already knowing) if there was a way to create such a chart without doubling the data and using table calculations instead. Well, Ann – you were (of course) right!
This blog post will guide you through the steps to create a Step Area Chart without any data prep – I hope you will enjoy this!
Any Superstore data will do!
Let’s demonstrate the general implementation concept with 2018 Superstore sales by month.
To create a Step Area Chart, you basically have to draw a Step Line manually (and then change the mark to area mark). To do this, we add for each month the previous sales to get the step line. (Make sure to check out Rody Zakovich‘s blogpost CREATE A STEP CHART IN TABLEAU WITHOUT DATA MODELING to learn more about this technique.)
IFNULL(ZN(SUM([Sales])) - LOOKUP(ZN(SUM([Sales])), -1),0)
[Previous Sales]+[Difference Sales]
With just these three calculations we are now able to draw our Step Area Chart:
To label my Step Area Charts, I like to create a dual-axis, where I choose the line mark, YEAR(Order Date) on Path and continuous MONTH(Order Date) on detail to create vertical lines for each month. You can then add sales to the label card and label only the line ends. This will only label the actual sales for each month.
The tricky part for the Step Area Chart is, that we cannot use Path to define the order, in which the marks have to be connected (previous sales first, then actual sales for each month). This is due to the missing Path card for the Area mark:
That’s why we have to use Sales Calculated instead of a simple sum(Sales). Both measures have identical values, but the Step Area Chart just won’t work with the latter.
Besides the labelling, you can also use the second axis for highlighting certain months, like required in this challenge.
Click the image to play with the interactive version on Tableau Public! Of course, you can also download the viz.
I hope you all enjoyed reading and that you will find own use cases for this. Please leave a comment below or reach out to me on Twitter @ProfDrKSchulte.