Question

我有一个dataFrame

[in] MyDates
[out]  
2017-04-04        -5.0
2017-04-03        -5.0
2017-03-31        -4.0
2017-03-30        -6.0
2017-03-29        -5.0
2017-03-28        -5.0

每个数字对应我应该在相应日期添加或删除的天数。我想创建一个新列，索引日期减去第一列中的天数。我知道我可以用DateOffset做到但我无法弄清楚如何......

谢谢！

Answer 1

您可以将列转换为TimedeltaIndex或to_timedelta和add（+）或减去(-)值：

df['new'] = df.index - pd.TimedeltaIndex(df['col'], unit='d')
print (df)
            col        new
2017-04-04 -5.0 2017-04-09
2017-04-03 -5.0 2017-04-08
2017-03-31 -4.0 2017-04-04
2017-03-30 -6.0 2017-04-05
2017-03-29 -5.0 2017-04-03
2017-03-28 -5.0 2017-04-02

或者：

df['new'] = df.index + pd.to_timedelta(df['col'], unit='d')
print (df)
            col        new
2017-04-04 -5.0 2017-03-30
2017-04-03 -5.0 2017-03-29
2017-03-31 -4.0 2017-03-27
2017-03-30 -6.0 2017-03-24
2017-03-29 -5.0 2017-03-24
2017-03-28 -5.0 2017-03-23

如果Series为input添加to_frame：

df = s.to_frame('date')
df['new'] = df.index - pd.TimedeltaIndex(df['date'], unit='d')
print (df)
            date        new
2017-04-04  -5.0 2017-04-09
2017-04-03  -5.0 2017-04-08
2017-03-31  -4.0 2017-04-04
2017-03-30  -6.0 2017-04-05
2017-03-29  -5.0 2017-04-03
2017-03-28  -5.0 2017-04-02

Answer 2

IIUC你要构建一个TimedeltaIndex并添加它：

In [173]:    
df.index + pd.TimedeltaIndex(df['days'], unit='d')

Out[173]:
DatetimeIndex(['2017-03-30', '2017-03-29', '2017-03-27', '2017-03-24',
               '2017-03-24', '2017-03-23'],
              dtype='datetime64[ns]', freq=None)

如果是专栏，您只需执行df['Dates'] + pd.TimedeltaIndex(df['days'], unit='d')

In [176]:
df['offset_date'] = df['Dates'] + pd.TimedeltaIndex(df['days'], unit='d')
df

Out[176]:
       Dates  days offset_date
0 2017-04-04  -5.0  2017-03-30
1 2017-04-03  -5.0  2017-03-29
2 2017-03-31  -4.0  2017-03-27
3 2017-03-30  -6.0  2017-03-24
4 2017-03-29  -5.0  2017-03-24
5 2017-03-28  -5.0  2017-03-23

如果它是索引并且您想要添加为列，那么它几乎是相同的操作：

In [180]:    
df['offset_date'] = df.index + pd.TimedeltaIndex(df['days'], unit='d')
df

Out[180]:
            days offset_date
Dates                       
2017-04-04  -5.0  2017-03-30
2017-04-03  -5.0  2017-03-29
2017-03-31  -4.0  2017-03-27
2017-03-30  -6.0  2017-03-24
2017-03-29  -5.0  2017-03-24
2017-03-28  -5.0  2017-03-23

DateOffset熊猫减法

2 个答案: