有人能带我看完这行代码吗？

Question

for col in cols_with_missing:
    imputed_X_train_plus[col + '_was_missing'] = imputed_X_train_plus[col].isnull()
    imputed_X_test_plus[col + '_was_missing'] = imputed_X_test_plus[col].isnull()

是什么

imputed_X_train_plus[col + '_was_missing']

什么意思？你知道吗

Answer 1

我要编造一些数据来说明。考虑

import numpy as np
import pandas as pd

imputed_X_train_plus = pd.DataFrame({'joe': [3, np.nan],
                                     'nick': [np.nan, 6],
                                     'fred': [1, 7]})

此时，imputed_X_train_plus是具有NaN值的数据帧。你知道吗

      joe   nick  fred
   0  3.0   NaN   1
   1  NaN   6.0   7

假设您知道哪些列缺少值。它们在cols_with_missing中。你知道吗

cols_with_missing = ['joe', 'nick']

现在您要标记出那些缺少的值。你也是

for col in cols_with_missing:
    imputed_X_train_plus[col +'_was_missing'] = imputed_X_train_plus[col].isnull()

现在你有了imputed_X_train_plus般的

   joe  nick  fred  joe_was_missing  nick_was_missing
0  3.0   NaN     1            False              True
1  NaN   6.0     7             True             False

总之，col + '_was_missing'创建了一个新的str（如joe_was_missing），用于插入imputed_X_train_plus的新列名。你知道吗