[英]Dataframe to extract 2 most recent rows of each group
一个简单的数据框,我想选择所有列的最新 2 行(按“年份”排序)。
import pandas as pd
data = {'People' : ["John","John","John","Kate","Kate","David","David","David","David"],
'Year': ["2018","2019","2006","2017","2012","2006","2019","2018","2017"],
'Sales' : [120,100,60,150,135,140,90,110,160]}
df = pd.DataFrame(data)
我在下面尝试过,但它没有产生想要的东西:
df = df.groupby('People')
df_1 = pd.concat([df.head(2)]).drop_duplicates().sort_values('Year').reset_index(drop=True)
什么是正确的写法? 谢谢你。
IIUC,使用pandas.DataFrame.nlargest
:
df['Year'] = df['Year'].astype(int)
df.groupby('People', as_index=False).apply(lambda x: x.nlargest(2, "Year"))
输出:
People Year Sales
0 6 David 2019 90
7 David 2018 110
1 1 John 2019 100
0 John 2018 120
2 3 Kate 2017 150
4 Kate 2012 135
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