Pandas：使用滚动函数检查 NaN

Question

我有一个带有变量 "A" 的数据框，我想创建一个滚动 Nan 检查器，这样新变量 "rolling_nan" = 1 if ALL 3 (seconds) cells (current cell 和前两个）是 NaN，否则 "rolling_nan" = 0.

我正在应用一个函数，因为 .rolling pandas 函数不支持 isna()。但是我得到以下信息。我也不确定如何在 NaN 检查器中包含相同的行值。

import pandas as pd
import numpy as np

idx = pd.date_range('2018-01-01', periods=10, freq='S')
df = pd.DataFrame({"A":[1,2,3,np.nan,np.nan,np.nan,6,7,8,9]}, index = idx)
df

def isna_func(x):
    return 1 if pd.isna(x).all() == True else 0
df['rolling_nan'] = df['A'].rolling(3).apply(isna_func)
df

                    A   rolling_nan
2018-01-01 00:00:00 1.0 NaN
2018-01-01 00:00:01 2.0 NaN
2018-01-01 00:00:02 3.0 0.0
2018-01-01 00:00:03 NaN NaN
2018-01-01 00:00:04 NaN NaN
2018-01-01 00:00:05 NaN NaN
2018-01-01 00:00:06 6.0 NaN
2018-01-01 00:00:07 7.0 NaN
2018-01-01 00:00:08 8.0 0.0
2018-01-01 00:00:09 9.0 0.0

在上面的示例中，rolling_nan 应仅在时间戳 2018-01-01 00:00:05 处等于 1，否则应等于 0。

Answer 1

你可以用不同的方式思考标记所有 notna ，然后找到 max

df.A.notna().rolling(3).max()==0
Out[316]: 
2018-01-01 00:00:00    False
2018-01-01 00:00:01    False
2018-01-01 00:00:02    False
2018-01-01 00:00:03    False
2018-01-01 00:00:04    False
2018-01-01 00:00:05     True
2018-01-01 00:00:06    False
2018-01-01 00:00:07    False
2018-01-01 00:00:08    False
2018-01-01 00:00:09    False
Freq: S, Name: A, dtype: bool

将其分配回去

df['rollingnan']=(df.A.notna().rolling(3).max()==0).astype(int)
df
Out[320]: 
                       A  rollingnan
2018-01-01 00:00:00  1.0           0
2018-01-01 00:00:01  2.0           0
2018-01-01 00:00:02  3.0           0
2018-01-01 00:00:03  NaN           0
2018-01-01 00:00:04  NaN           0
2018-01-01 00:00:05  NaN           1
2018-01-01 00:00:06  6.0           0
2018-01-01 00:00:07  7.0           0
2018-01-01 00:00:08  8.0           0
2018-01-01 00:00:09  9.0           0

或根据自己的想法使用 all

df['A'].isna().rolling(3).apply(lambda x : x.all(),raw=True)
Out[323]: 
2018-01-01 00:00:00    NaN
2018-01-01 00:00:01    NaN
2018-01-01 00:00:02    0.0
2018-01-01 00:00:03    0.0
2018-01-01 00:00:04    0.0
2018-01-01 00:00:05    1.0
2018-01-01 00:00:06    0.0
2018-01-01 00:00:07    0.0
2018-01-01 00:00:08    0.0
2018-01-01 00:00:09    0.0
Freq: S, Name: A, dtype: float64

Pandas：使用滚动函数检查 NaN

Pandas: Checking for NaN using rolling function

pandas

apply

nan

rolling-computation