KNOWLEDGE BASE

Forecast Shows Flat Line


Published: 19 Apr 2013
Last Modified Date: 16 Sep 2019

Issue

When a forecast is enabled, the forecast may be a flat line. In a crosstab view, all forecast values would be identical.

Environment

Tableau Desktop

Resolution

Try some or all of the below troubleshooting steps as appropriate. The best solution will vary depending on your data. 
  • Add more data to the view. In general, the more data points you have in your time series, the better the resulting forecast will be. Having enough data is particularly important if you want to model seasonality, because the model is more complicated and requires more proof in the form of data to achieve a reasonable level of precision.
  • Change the date level in the view. Tableau tests for a seasonal cycle with the length most typical for the time aggregation of the time series for which the forecast is estimated. For example, if you aggregate by months, Tableau will look for a 12-month cycle.
  • Aggregate by a more granular date level. If the date level in the view, and the desired date level to use for the forecast model is more granular (e.g. days are more granular than months), then the forecast model can be modifed
    1. Right-click the forecast, and select Forecast > Forecast Options…
    2. In the Forecast Options dialog box, under Aggregate by, select a more granular date level
  • Verify that the forecast model includes seasonality. If the data has a seasonal trend, but the forecast model is "Automatic without seasonality" or "Custom" with Season set to "None", then Tableau Desktop will not detect the seasonal trend.
    1. Right-click the forecast, and select Forecast > Forecast Options…
    2. In the Forecast Options dialog box, under Forecast Model select Automatic.

Cause

When Tableau Desktop cannot derive a meaningful forecast with the data in view and the configuration of the forecast, a flat line is displayed.

 
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