对 DatetimeIndexResampler 类型执行操作时出错

Question

我有一个时间序列数据框，想找出每条记录中的日期与该数据框中的最后一个（最大）日期之间的差异。但出现错误 - TypeError：不支持的操作数类型 -：'DatetimeIndex' 和 'SeriesGroupBy'。从错误看来，数据框不是允许这些操作允许的“正确”类型。我怎样才能避免这种情况或可能将数据转换为其他格式才能进行操作。下面是重现错误的示例代码

import pandas as pd

df = pd.DataFrame([[54.7,36.3,'2010-07-20'],[54.7,36.3,'2010-07-21'],[52.3,38.7,'2010-07-26'],[52.3,38.7,'2010-07-30']],
                  columns=['col1','col2','date'])
df.date = pd.to_datetime(df.date)
df.index = df.date
df = df.resample('D')
print(type(df))
diff = (df.date.max() - df.date).values

Answer 1

我认为您需要先由DataFrame.set_index 创建DatetimeIndex，所以如果通过max 聚合则得到连续值：

df = pd.DataFrame([[54.7,36.3,'2010-07-20'],
                   [54.7,36.3,'2010-07-21'],
                   [52.3,38.7,'2010-07-26'],
                   [52.3,38.7,'2010-07-30']],
              columns=['col1','col2','date'])

df.date = pd.to_datetime(df.date)

df1 = df.set_index('date').resample('D').max()
#alternative if not duplicated datetimes
#df1 = df.set_index('date').asfreq('D')
print (df1)
            col1  col2
date                  
2010-07-20  54.7  36.3
2010-07-21  54.7  36.3
2010-07-22   NaN   NaN
2010-07-23   NaN   NaN
2010-07-24   NaN   NaN
2010-07-25   NaN   NaN
2010-07-26  52.3  38.7
2010-07-27   NaN   NaN
2010-07-28   NaN   NaN
2010-07-29   NaN   NaN
2010-07-30  52.3  38.7

然后将索引的最大值与自身相减，并将 timedeltas 转换为天数 TimedeltaIndex.days：

df1['diff'] =  (df1.index.max() - df1.index).days
print (df1)
            col1  col2  diff
date                        
2010-07-20  54.7  36.3    10
2010-07-21  54.7  36.3     9
2010-07-22   NaN   NaN     8
2010-07-23   NaN   NaN     7
2010-07-24   NaN   NaN     6
2010-07-25   NaN   NaN     5
2010-07-26  52.3  38.7     4
2010-07-27   NaN   NaN     3
2010-07-28   NaN   NaN     2
2010-07-29   NaN   NaN     1
2010-07-30  52.3  38.7     0