python - 使用 Python 中的 Pandas，为每个组选择最高值的行

Question

使用 Pandas，对于以下数据集

author1,category1,10.00
author1,category2,15.00
author1,category3,12.00
author2,category1,5.00
author2,category2,6.00
author2,category3,4.00
author2,category4,9.00
author3,category1,7.00
author3,category2,4.00
author3,category3,7.00

我想得到每个作者的最高值

author1,category2,15.00
author2,category4,9.00
author3,category1,7.00
author3,category3,7.00

(抱歉，我是 Pandas 菜鸟。)

Answer 1

import pandas as pd

df = pd.read_csv("in.csv", names=("Author","Cat","Val"))

print(df.groupby(['Author'])['Val'].max())

获取df:

inds = df.groupby(['Author'])['Val'].transform(max) == df['Val']
df = df[inds]
df.reset_index(drop=True, inplace=True)
print(df)
    Author        Cat  Val
0  author1  category2   15
1  author2  category4    9
2  author3  category1    7
3  author3  category3    7