[英]Forward fill missing values by group after condition is met in pandas
I'm having a bit of trouble with this.我对此有点麻烦。 My dataframe looks like this:
我的 dataframe 看起来像这样:
id amount dummy
1 130 0
1 120 0
1 110 1
1 nan nan
1 nan nan
2 nan 0
2 50 0
2 20 1
2 nan nan
2 nan nan
So, what I need to do is, after the dummy gets value = 1, I need to fill the amount variable with zeroes for each id
, like this:所以,我需要做的是,在 dummy 获得 value = 1 之后,我需要为每个
id
填充 amount 变量为零,如下所示:
id amount dummy
1 130 0
1 120 0
1 110 1
1 0 nan
1 0 nan
2 nan 0
2 50 0
2 20 1
2 0 nan
2 0 nan
I'm guessing I'll need some combination of groupby('id')
, fillna(method='ffill')
, maybe a .loc
or a shift()
, but everything I tried has had some problem or is very slow.我猜我需要
groupby('id')
, fillna(method='ffill')
,也许是.loc
或shift()
的某种组合,但我尝试的一切都有一些问题或非常慢。 Any suggestions?有什么建议么?
The way I will use我将使用的方式
s = df.groupby('id')['dummy'].ffill().eq(1)
df.loc[s&df.dummy.isna(),'amount']=0
You can do this much easier:你可以更容易地做到这一点:
data[data['dummy'].isna()]['amount'] = 0
This will select all the rows where dummy is nan and fill the amount column with 0.这将 select 所有 dummy 为 nan 的行并用 0 填充金额列。
IIUC, ffill()
and mask the still-nan: IIUC、
ffill()
和掩码 Still-nan:
s = df.groupby('id')['amount'].ffill().notnull()
df.loc[df['amount'].isna() & s, 'amount'] = 0
Output: Output:
id amount dummy
0 1 130.0 0.0
1 1 120.0 0.0
2 1 110.0 1.0
3 1 0.0 NaN
4 1 0.0 NaN
5 2 NaN 0.0
6 2 50.0 0.0
7 2 20.0 1.0
8 2 0.0 NaN
9 2 0.0 NaN
Could you please try following.请您尝试以下操作。
df.loc[df['dummy'].isnull(),'amount']=0
df
Output will be as follows. Output 如下。
id amount dummy
0 1 130.0 0.0
1 1 120.0 0.0
2 1 110.0 1.0
3 1 0.0 NaN
4 1 0.0 NaN
5 2 NaN 0.0
6 2 50.0 0.0
7 2 20.0 1.0
8 2 0.0 NaN
9 2 0.0 NaN
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