数据框-在按日期分组的行中查找前0

Question

我每天都有多个数据点。我需要检测每天的前0个。我想将数据转换为输出列。

可重现格式的数据：

Date,Data,Output
1/1/2019,1,False
1/1/2019,1,False
1/1/2019,0,True
1/1/2019,0,False
1/1/2019,1,False
2/1/2019,1,False
2/1/2019,0,True
2/1/2019,1,False
3/1/2019,0,True
3/1/2019,0,False

我认为这可能涉及groupby功能，但努力弄清楚如何开始。

Answer 1

使用duplicated：

df["output"] = ~(df[df["Data"]==0].duplicated(subset=["Date","Data"],keep="first"))
df["output"].fillna(False, inplace=True)

print (df)

#
        Date  Data  output
0  1/01/2019     1   False
1  1/01/2019     1   False
2  1/01/2019     0    True
3  1/01/2019     0   False
4  1/01/2019     1   False
5  2/01/2019     1   False
6  2/01/2019     0    True
7  2/01/2019     1   False
8  3/01/2019     0    True
9  3/01/2019     0   False

Answer 2

尝试2个布尔型口罩

m = df.Data.eq(0)
m1 = m.groupby(df.Date).cumsum().eq(1)    
df['New'] = m & m1

Out[834]:
        Date  Data    New
0  1/01/2019     1  False
1  1/01/2019     1  False
2  1/01/2019     0   True
3  1/01/2019     0  False
4  1/01/2019     1  False
5  2/01/2019     1  False
6  2/01/2019     0   True
7  2/01/2019     1  False
8  3/01/2019     0   True
9  3/01/2019     0  False

Answer 3

另一个使用loc的groupby解决方案

df.loc[df[df.data.eq(0)].groupby('date').data.idxmin(), 'out'] = True
df = df.fillna(False)