Gantt charts are most commonly used in project management as these charts show various activities and tasks with the time required to complete those tasks. Gantt charts are even more useful when they show dependencies among various tasks. This type of chart is very helpful when the number of activities is low (around 20-30), otherwise the chart becomes too big to be understood easily.
Let's use the sample file Sample – Superstore Sales (Excel). Open a new worksheet and select Sample – Superstore Sales (Excel) as the data source.
Once the data is loaded, perform the following steps to create a Gantt chart:
- Click on Analysis from the top menu toolbar, and if Aggregate Measures is checked, click on it again to uncheck that option.
- Click on the Show Me button to bring the Show Me toolbar on the screen.
- While holding the Ctrl key, click on Order Date and Category (under Products) from Dimensions and Time to Ship from Measures.
- Click on the Gantt chart icon on the Show Me toolbar.
- Drag-and-drop Order Date into the Filters pane.
- Select Years from the Filter Field [Order Date] options dialog box and hit Next.
- Check 2012 from the list and hit OK.
- Right-click on YEAR(Order Date) on the Columns shelf and select the Day May 8, 2011 option.
- Drag-and-drop Order Date into the Filters pane.
- Select Months from the Filter Field [Order Date] options dialog box and hit Next.
- Check December from the list and hit OK.
- Drag-and-drop Region from Dimensions into the Color Marks input box.
- Drag-and-drop Region from Dimensions into the Rows shelf before Category. The generated Gantt chart should look like the one in the following screenshot:
Representing time this way helps the reader to discern which activity took the longest amount of time. We added the Order Date field two times in the Filters pane to first filter for the year 2012 and then for the month of December. In this recipe, out of all the products shipped in December of 2012, we can easily see the red bars for the West region in the Office Supplies category is longer, suggesting that these products took the longest amount of time to ship.
Andy Kriebel, a Tableau data visualization expert, has a great example of Gantt charts using US presidential data. The following link shows the lengths of terms in office of Presidents from various parties:
http://vizwiz.blogspot.com/2010/09/tableau-tip-creating-waterfall-chart.html