I’ve noticed waterfall charts are becoming quite fashionable now. If you’re not sure why this is used, it’s a great way, for example, of showing how total revenue is compiled from it’s components. Using the Tableau Gantt Chart it’s quite simple to build. In this article I’ll give a very quick guide to building your own such as the chart below.
The dataset I’m using is very simple – it only contains Product and Revenue. The first thing I do is drag the Product to the Columns shelf and the Revenue to the Rows. Next change the chart type to a Gantt Bar. This will give you the following:
As you can see this looks a long way off the finished article – but there’s only a few more steps. The next step is to get the bars running after each other and filled in – which means table calculations and a calculated field.
First create a Running Total table calculation on the SUM(Revenue) pill. The next step is to fill in the bars. This requires a calculated field which just takes the negative of the revenue. In this case the formula for the calculated field is [Revenue] * -1
Drag this calculated field on to the the Size shelf and the bars will fill out. Next we want to colour these bars to a positive number is a different colour to a negative. This requires another calculated field. The formula is IF SUM([Revenue]) >= 0 THEN 1 ELSE -1 END, in other word giving all +ve numbers a different value to the -ve. Drag this field on to the Colour shelf. Your chart should now look like the following:
The final step is to switch on the Grand Totals. In Tableau 7 this is on the toolbar under Analysis – Totals – Show Row Grand Totals. In Tableau 6 I think it’s under the Table menu on the toolbar.