There may be several circumstances where we need to read historical data and to extrapolate this historical data to get an approximate idea of what to expect in the future. These forecasted values can help us in, say, budget planning or even redefining our current strategies.
The forecasting functionality in Tableau uses an built-in statistical model that enables us to estimate future values by extrapolating historical data while also taking trend and seasonality into consideration. Among the various models that are available for forecasting, Tableau uses the exponential smoothing model.
An important point to remember is that there are plenty of external factors that govern the actual data and hence the forecast will give us an approximate idea of what to expect in future. The accuracy of this forecast however will depend on the quality of the historical data.
In order to enable the forecasting functionality in Tableau, let's continue working in our existing workbook and use the Order Date and Profit fields from the Orders data from Sample - Superstore Subset.xlsx.
Let's see how to do forecasting in Tableau:
- Let us create a new sheet and rename it
Forecasting. - Select the Orders (Sample - Superstore) data source from the Data pane to see the Dimensions and Measures for that data source. Refer to the following screenshot:
- Next, let us right-click and drag Order Date from the Dimensions pane, drop it into the Columns shelf, and select the MONTH(Order Date) option as shown in the following screenshot:
- Let us then drag and drop Profit into the Rows shelf and our view will update as shown in the following screenshot:
- We will the click on the Analytics pane, which is next to the Data pane, and then drag the Forecast option from the Model pane over to the chart. Refer the following screenshot:
- Our view will now update to the following:
- Now, in the preceding screenshot, we can see that the dark blue color is our actual Profit whereas the light blue color is the estimated or forecasted Profit. However, the estimated Profit is a straight line and it may not be giving us an accurate picture, so let's see if we can change that. We will select Forecast Options… via the Analysis | Forecast option in the toolbar. Refer to the following screenshot:
- Once we do that, we will get a new dialog box, where we will keep most of the default selections as-is; we will only make changes in the Forecast Model section as shown in the following screenshot:
- After we change the Forecast Model from Automatic to Custom, our dialog box will update as shown in the following screenshot:
- Next, we will click on the Trend and Season drop-downs and select the Additive option in both. Refer to the following screenshot:
- When we select OK after selecting the Additive option from both the Trend and Season drop-down, our view will update as shown in the following screenshot:
In the previous screenshot, the dark blue line is the actual Profit whereas the light blue line is the estimated Profit. Further, the light blue band is the 95% prediction interval, which can be changed to either 90% or 99%. Refer to the following screenshot:
In the previous example, Tableau is reading our historic data from January 2011 to November 2014 and creating a forecast through December 2015 while looking for potential seasonal patterns every 12 months. In the previous recipe, when we selected the Additive option for Trend and Season, we indicated to Tableau that our business is subject to seasonality. However, if we wish to look for more information, we can select the Describe Forecast… option via Analysis | Forecast in the toolbar. Refer to the following screenshot:
Once we do that, we will get a new dialog box as shown in the following screenshot:
In the previous recipe, we saw how to do a quick forecast. To learn more about the forecasting functionality in Tableau, refer to the following link:
http://onlinehelp.tableau.com/current/pro/desktop/en-us/forecasting.html