[英]GroupBy one column, custom operation on another column of grouped records in pandas
I wanted to apply a custom operation on a column by grouping the values on another column. 我想通过将值分组到另一列上来对列应用自定义操作。 Group by column to get the count, then divide the another column value with this count for all the grouped records.
按列分组以获取计数,然后将所有分组记录的另一列值除以此计数。
My Data Frame: 我的数据框架:
emp opp amount
0 a 1 10
1 b 1 10
2 c 2 30
3 b 2 30
4 d 2 30
My scenario: 我的情景:
Final Output DataFrame: 最终输出数据框架:
emp opp amount
0 a 1 5
1 b 1 5
2 c 2 10
3 b 2 10
4 d 2 10
What is the best possible to do so 什么是最好的可能
df['amount'] = df.groupby('opp')['amount'].transform(lambda g: g/g.size)
df
# emp opp amount
# 0 a 1 5
# 1 b 1 5
# 2 c 2 10
# 3 b 2 10
# 4 d 2 10
Or: 要么:
df['amount'] = df.groupby('opp')['amount'].apply(lambda g: g/g.size)
does similar thing. 做类似的事情。
You could try something like this: 你可以尝试这样的事情:
df2 = df.groupby('opp').amount.count()
df.loc[:, 'calculated'] = df.apply( lambda row: \
row.amount / df2.ix[row.opp], axis=1)
df
Yields: 产量:
emp opp amount calculated
0 a 1 10 5
1 b 1 10 5
2 c 2 30 10
3 b 2 30 10
4 d 2 30 10
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