As we've seen, trend models make predictions. Given a good model, you expect additional data to follow the trend. When the trend is over time, you can get some idea of where future values may fall. However, predicting future values often requires a different type of model. Factors such as seasonality can make a difference not predicted by a trend alone. Starting with version 8.0, Tableau includes built-in forecasting models that can be used to predict and visualize future values.
To use forecasting, you'll need a view that includes a date field or enough date parts for Tableau to reconstruct a date (for example, a Year and a Month field). Tableau 10 also allows for forecasting based on integers instead of dates. You may drag and drop a Forecast from the Analytics pane, navigate to Analysis | Forecast | Show Forecast from the menu, or right click the view's pane and select the option from the context menu.
Here, for example is the view of the population growth over time of Afghanistan...
