滚动字符串变量 [英] rolling with string variables

问题描述

考虑此示例

import pandas as pd
import numpy as np

df = pd.DataFrame({'mytime' : [pd.to_datetime('2018-01-01 14:34:12.340'),
                             pd.to_datetime('2018-01-01 14:34:13.0'),
                             pd.to_datetime('2018-01-01 14:34:15.342'),
                             pd.to_datetime('2018-01-01 14:34:16.42'),
                             pd.to_datetime('2018-01-01 14:34:28.742')],
                    'myvalue' : [1,2,np.NaN,3,1],
                    'mychart' : ['a','b','c','d','e']})

df.set_index('mytime', inplace = True)

df
Out[15]: 
                        mychart  myvalue
mytime                                  
2018-01-01 14:34:12.340       a      1.0
2018-01-01 14:34:13.000       b      2.0
2018-01-01 14:34:15.342       c      NaN
2018-01-01 14:34:16.420       d      3.0
2018-01-01 14:34:28.742       e      1.0

在这里，我想使用最近 2秒(而不是最后两个观察值)中的值concatenate mychart中的字符串.

Here I want to concatenate the strings in mychart using the values in the last 2 seconds (not the last two observations).

不幸的是，下面的两次尝试都失败了

Unfortunately, both attempts below fail miserably

df.mychart.rolling(window = '2s', closed = 'right').apply(lambda x: ' '.join(x), raw = False)
df.mychart.rolling(window = '2s', closed = 'right').apply(lambda x: (x + ' ').cumsum(), raw = False)

TypeError: cannot handle this type -> object

我们终于达到了Pandas 23.4可以做什么的极限吗? :) 谢谢！

Are we finally hitting the limits of what Pandas 23.4 can do? :) Thanks!

推荐答案

df.Rolling似乎不支持此功能.相反，您是否可以每隔1秒重新采样一次，然后将每个值与其后的行连接起来?

It doesn't look like df.Rolling will support this. Instead, can you resample to 1 sec intervals and then just concat every value with the row after it?

然后您可以使用merge_asof将结果合并回去:

You can then merge the result back using merge_asof:

v = df.resample('1s').agg(''.join)
pd.merge_asof(df, 
              v.add(v.shift(-1)).rename({'mychart': 'res'}, axis=1), 
              left_index=True, 
              right_index=True)

                         myvalue mychart  res
mytime                                       
2018-01-01 14:34:12.340      1.0       a   ab
2018-01-01 14:34:13.000      2.0       b    b
2018-01-01 14:34:15.342      NaN       c   cd
2018-01-01 14:34:16.420      3.0       d    d
2018-01-01 14:34:28.742      1.0       e  NaN

这篇关于滚动字符串变量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！