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[英]Compare a value to the value in the previous row and assign a value to another column (Pandas) - how to speed up?
[英]Pandas assign a column value basis previous row different column value
使用cumsum
:
df["Available"] = df["Supply"].cumsum() - df["Order"].cumsum()
df["Supply"] = df["Available"] + df["Order"]
>>> df
product Month Order Supply Available
0 xx-xxx 202107 718 1531.0 813.0
1 None 202108 668 813.0 145.0
2 None 202109 5030 2306.0 -2724.0
3 None 202110 667 -2724.0 -3391.0
使用cumsum
計算正確的值:
假設:
# Setup
data = {'Product': ['xx-xxx', 'xx-xxx', 'xx-xxx', 'xx-xxx'],
'Month': [202107, 202108, 202109, 202110],
'Order': [718, 668, 5030, 667],
'Supply': [1531, 0, 2161, 0],
'Available': [813, -668, -2869, -667]}
df = pd.DataFrame(data)
df[['Supply', 'Available']] = df.groupby('Product').apply(lambda x: \
pd.DataFrame({'Supply': x['Order'] + x['Supply'].cumsum() - x['Order'].cumsum(),
'Available': x['Supply'].cumsum() - x['Order'].cumsum()}))
Output:
>>> df
Product Month Order Supply Available
0 xx-xxx 202107 718 1531 813
1 xx-xxx 202108 668 813 145
2 xx-xxx 202109 5030 2306 -2724
3 xx-xxx 202110 667 -2724 -3391
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