Python

Question

所以我有类似这样的数据：

import pandas as pd
df = pd.DataFrame({'Order ID':[555,556,557,558,559,560,561,562,563,564,565,566],
                   'State':["MA","MA","MA","MA","MA","MA","CT","CT","CT","CT","CT","CT"],
                   'County':["Essex","Essex","Essex","Worcester","Worcester","Worcester","Bristol","Bristol","Bristol","Hartford","Hartford","Hartford"],
                   'AP':[50,50,75,100,100,125,150,150,175,200,200,225]})

但我需要添加一个列来显示按州和县分组的 AP 模式。我可以通过这种方式获得模式：

(df.groupby(['State', 'County']).AP.agg(Mode = (lambda x: x.value_counts().index[0])).reset_index().round(0))

我只是不确定如何将该数据添加到原始数据中，使其看起来像这样：

Order ID	State	County	AP	Mode
555	MA	Essex	50	50
556	MA	Essex	50	50
557	MA	Essex	75	50
558	MA	Worcester	100	100
559	MA	Worcester	100	100
560	MA	Worcester	125	100
561	CT	Bristol	150	150
562	CT	Bristol	150	150
563	CT	Bristol	175	150
564	CT	Hartford	200	200
565	CT	Hartford	200	200
566	CT	Hartford	225	200

Answer 1

对新列使用 GroupBy.transform：

df['Mode'] = (df.groupby(['State', 'County']).AP
                .transform(lambda x: x.value_counts().index[0]))

或Series.mode:

df['Mode'] = df.groupby(['State', 'County']).AP.transform(lambda x: x.mode().iat[0])

Python - 添加分组模式作为原始数据集中的附加列

Python - Adding grouped mode as additional column in original dataset

pandas

mode

group