同时，添加了时间窗口功能。看到这个链接。
In [1]: df = Dataframe({'B': range(5)})In [2]: df.index = [Timestamp('20130101 09:00:00'), ...: Timestamp('20130101 09:00:02'), ...: Timestamp('20130101 09:00:03'), ...: Timestamp('20130101 09:00:05'), ...: Timestamp('20130101 09:00:06')]In [3]: dfOut[3]:B2013-01-01 09:00:00 02013-01-01 09:00:02 12013-01-01 09:00:03 22013-01-01 09:00:05 32013-01-01 09:00:06 4In [4]: df.rolling(2, min_periods=1).sum()Out[4]: B2013-01-01 09:00:00 0.02013-01-01 09:00:02 1.02013-01-01 09:00:03 3.02013-01-01 09:00:05 5.02013-01-01 09:00:06 7.0In [5]: df.rolling('2s', min_periods=1).sum()Out[5]: B2013-01-01 09:00:00 0.02013-01-01 09:00:02 1.02013-01-01 09:00:03 3.02013-01-01 09:00:05 3.02013-01-01 09:00:06 7.0
