The Forecast analysis enables you to add your own values to a series. The forecasting method allows the user to add both future values and overwrite historical ones. Forecasts can also be added in Series list, but this means that the forecasts will be applied to the raw data prior to any analyses. By using forecast analysis, values can be added as an intermediate step in the overall analysis.
When you press 'Edit', you will see a dialog where you can specify forecast values and specify how they should be added. 'Value method' lets you specify if the forecast should be added as an absolute value or be dependent on some other value either as a difference or as a percentage change from said value.
Date method gives you the option of defining forecasts both at a specific point in time and at a specific time horizon forward in time from the last observation or forecast.
If a row in edit contains both an observation and a forecast, this option lets you choose which value to include in the output.
Here, you specify how the calculation treats missing values.
In this example, we added forecasts to the quarterly changes in the GDP of France.
- How to add a forecast values?
- How to remove a forecast?
- How to disable the special presentation of forecast values?
- How to add forecast before the start of time series?
You can add forecast values to a raw time series in the Series list, or after having applied some calculations to it.
Add a forecast in the beginning of the document
To add a forecast to the raw time series, before any calculations are made, click on Series list in the analysis tree. Open the tab called Forecasts and click Edit next to the series you'd like to add a forecast to.
Please note that these forecasts will be added on the original frequency of the time series, even if the document uses another frequency.
Add a forecast after calculations
To add the forecast after having applied some calculations to it, add the forecast as an analysis later in the analysis tree.
Depending how you want to proceed, there are two solutions. You can:
- remove the forecast values entirely from a series
- keep the values and remove the forecast indicator for them
To remove forecast values entirely, use the following expression in Series list. It replaces forecast values with null and returns only the non-forecast values of the series.
if(isForecast(series), Null(), series)
To remove the forecast indicator from a series, use the following expression in Series list. It returns the series values as non-forecast values when the condition (the second parameter) is false.
Forecast values are usually displayed in a different color on charts, so removing the forecast indicator will make the entire series be graphed in the same color.
Forecast values are usually presented with a distinct style on charts. If you do not want to make a visual distinction of forecasted values, there are two main ways you can do this.
- Remove the 'forecast flag' from all values in the series. (see above to question How to remove a forecast? for more information)
- Change the graph presentation so that forecasted values look the same as those that are not forecasts
To do this select the graph in the chart you'd like to change. Under Presentation properties, change the graph style from Automatic to Custom, and click on Forecast. Here, you can change the forecast color to match that of non-forecast values.
It's not possible. You can append values from another series with one of the join() formulas. For more information about this, click here: Joining with formula