ความใหม่ของการบริจาค

# Reference date to calculate the recency
reference_date = datetime.date(____, ____, ____)

# Select gifts made before the reference date
gifts_before_reference = gifts[(gifts["date"] < ____)]

# Latest gift per donor in 2017
last_gift = gifts_before_reference.groupby(["____"])["____"].____().reset_index()
last_gift["recency"] = ____ - ____["____"]   

# Add recency to the basetable
basetable = pd.merge(____, ____[["id", "recency"]], how="____")