You can extend a series with its last value or with a specific value.
Extend with last value to the end of a period
The following formulas, which you can type into the series list, will extend the input series to the end of the corresponding period:
If you want to mark the extended values as forecasts, use:
Extend with another value to a specified date
Using the formula below, you can customize what value is used and until when the series is extended.
Extend(series, observation, number)
You should input the series that you want to extend, the observation number where the extension should stop, and the value that should be used.