In the document of pandas.DataFrame.ewm, it says alpha = 2/(span + 1). Don't understand why such formula exists between alpha and span.
- Is it a convention or any sources to explain the formula?
- Is it only an assumption/setting in pandas? actually it can be other formats, e.g. alpha = 4/(span + 3)?
Googled but there is no clue on that.
Grateful if someone could help! Thx.
https://pandas.pydata.org/docs/reference/api/pandas.DataFrame.ewm.html#pandas-dataframe-ewm