Python填充了timedelta

Question

熊猫数据的标准填充方法允许限制矩阵中的下一个k项。现在，我不想用条目的数量来限制它，而是在一定的时间内限制它(我的索引是DatetimeIndex)。我的想法是，这些值有一种衰变，所以我想向前填充这些值，而不是用半个小时来填充NAs，但不要再往前写。我该怎么解决呢？

index                  value_a   value_b    diff
2016-01-01 00:01:00      2.8       NaN       NaN
2016-01-01 00:06:00      2.8       5.4      -2.6
2016-01-01 00:11:00      NaN       5.4       NaN
2016-01-01 00:16:00      NaN       NaN       NaN
2016-01-01 00:21:00      NaN       5.4       NaN

例如，在该示例中，我希望在未来的14分钟内替换NaN值，以便在value_a列中的00:21:00，NaN保持不变，而value_a和value_b的其他NaN消失。

Answer 1

如果是重采样，可以使用resample + transform和聚合first

#for testing 10Min
df = df.resample('10Min').transform('first')
print (df)
                     value_a  value_b  diff
index                                      
2016-01-01 00:01:00      2.8      5.4  -2.6
2016-01-01 00:06:00      2.8      5.4  -2.6
2016-01-01 00:11:00      NaN      5.4   NaN
2016-01-01 00:16:00      NaN      5.4   NaN
2016-01-01 00:21:00      NaN      5.4   NaN

或者可能需要transform + ffill

df = df.resample('10T').transform('ffill')
print (df)
                     value_a  value_b  diff
index                                      
2016-01-01 00:01:00      2.8      NaN   NaN
2016-01-01 00:06:00      2.8      NaN   NaN
2016-01-01 00:11:00      2.8      5.4  -2.6
2016-01-01 00:16:00      2.8      5.4  -2.6
2016-01-01 00:21:00      NaN      5.4   NaN