Pie charts and their variations are one of the most controversial types of charts. Many experts in the information graphics and information visualization fields have warned against the use of pie charts but they are still quite common in business presentations as well as reports. There are a few key things to consider while creating such a graphic:
- Limit the number of slices to three to four. In addition, slices must be large enough for easy differentiation.
- Limit the use of color (if there are only three to four slices to show, it is easy to use one color with different hues). Colors are better used only for differentiating one item from another and not for decorating. If many colors are used, the reader faces the difficulty of distinguishing items by color.
- Start the largest slice at 12 o'clock and move to the right; next to it on the left must be the next biggest slice. The smallest slice should be close to the bottom. This helps the reader see the bigger slices and make comparisons easily.
- Do not use any 3D pie charts as they make matters worse. Tableau saves the users from this trouble as 3D pie charts are not supported.
- Do not allow a sliced pie section to be sliced further, as it distracts the reader. Again, Tableau does not support exploding a slice.
- Make sure that the pie totals up to 100 percent of the measure; any other total will render the pie meaningless. For example, if you want to plot the profit by store location, the pie should total to the total profit by all stores; that is, 100 percent of the profit.
- Avoid excessive labels on the slices. Although labels will remove any guessing by the reader, if you label all the slices, then perhaps it is better if you replace the chart with a table.
Let's use the sample file Sample – Coffee Chain (Access). Open a new worksheet and select Sample – Coffee Chain (Access) as the data source.
Once the data is loaded, perform the following steps to create a simple pie chart:
- Drag-and-drop Profit into the Size box in the Marks pane.
- Drag-and-drop Market into the Rows shelf.
- Click on the Show Me button to make the toolbar visible.
- Click on the pie chart icon to create the pie chart.
- Right-click on SUM(Profit) in the Angle box in the Marks pane and hit Remove.
- To make the chart bigger, click on the zoom slider that can be seen after clicking the Size mark box.
Tableau's settings for default colors for pie charts as well as the setting for the placement of the various slices creates good-looking and effective pie charts; however, by tweaking colors and adjusting sizes, we can make the charts even better. The topic of changing color palettes is covered later in this book.