LibreOffice 7.2 ヘルプ

Returns the number of samples in period as calculated by Calc in case of FORECAST.ETS functions when argument period_length equals 1.

The same result is returned with FORECAST.ETS.STAT functions when argument stat_type equals 9 (and period_length equals 1).

FORECAST.ETS.SEASONALITY (values, timeline, [data_completion], [aggregation])

=FORECAST.ETS.SEASONALITY(Values;Timeline;TRUE();1)

Returns 6, the number of samples in period based on Values and Timeline named ranges above, no missing data, and AVERAGE as aggregation.