Actual dataframe consist of more than a million rows.
Say for example a dataframe is:
UniqueID Code Value OtherData
1 A 5 Z01
1 B 6 Z02
1 C 7 Z03
2 A 10 Z11
2 B 11 Z24
2 C 12 Z23
3 A 10 Z21
4 B 8 Z10
I want to obtain ratio of A/B for each UniqueID and put it in a new dataframe. For example, for UniqueID 1, its ratio of A/B = 5/6.
What is the most efficient way to do this in Python?
Want:
UniqueID RatioAB
1 5/6
2 10/11
3 Inf
4 0
Thank you.
One approach is using pivot_table
, aggregating with the sum
in the case there are multiple occurrences of the same letters (otherwise a simple pivot will do), and evaluating on columns A
and B
:
df.pivot_table(index='UniqueID', columns='Code', values='Value', aggfunc='sum').eval('A/B')
UniqueID
1 0.833333
2 0.909091
3 NaN
4 NaN
dtype: float64
If there is maximum one occurrence of each letter per group:
df.pivot(index='UniqueID', columns='Code', values='Value').eval('A/B')
UniqueID
1 0.833333
2 0.909091
3 NaN
4 NaN
dtype: float64
If you only care about A/B ratio:
df1 = df[df['Code'].isin(['A','B'])][['UniqueID', 'Code', 'Value']]
df1 = df1.pivot(index='UniqueID',
columns='Code',
values='Value')
df1['RatioAB'] = df1['A']/df1['B']
最明显的方式是通过 groupby。
df.groupby('UniqueID').apply(lambda g: g.query("Code == 'A'")['Value'].iloc[0] / g.query("Code == 'B'")['Value'].iloc[0])
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