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livc
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pandas 中如何让一列日期减去同一个日期?

  •  
  •   livc
    livc Sep 1, 2016 5008 views
    This topic created in 3533 days ago, the information mentioned may be changed or developed.
     time loc 0 2014-12-08 18 ad 1 2014-12-09 12 as 2 2014-12-12 12 xs 

    处理为

     time loc 0 1 ad 1 2 as 2 5 xs 

    其中 "2014-12-08 18" 代表 14 年 12 月 8 日的 18 点,想把时间这列更新为从12 月 8 日算起的第X天,应该如何操作?

    9 replies    2018-04-09 17:42:39 +08:00
    aaronzjw
        1
    aaronzjw  
       Sep 1, 2016
    import time 应该可以吧
    20150517
        2
    20150517  
       Sep 2, 2016 via iPhone
    apply
    wickila
        3
    wickila  
       Sep 2, 2016   1
    import pandas as pd
    import datetime


    def date2day(x):
    sd = datetime.datetime.strptime('2014-12-08 0', '%Y-%M-%d %H')
    d = datetime.datetime.strptime(x['time'], '%Y-%M-%d %H')
    x['time'] = (d - sd).days + 1
    return x


    df = pd.DataFrame([['2014-12-08 18', 'ad'], ['2014-12-09 12', 'as'], ['2014-12-12 12', 'xs']], columns=['time', 'loc'])
    df = df.apply(date2day, axis=1)

    print df
    xixijun
        4
    xixijun  
       Sep 2, 2016
    df['date_diff']=df['time'].diff().fillna(0)+pd.Timedelta('1 days')
    livc
        5
    livc  
    OP
       Sep 2, 2016
    @wickila 请问是否有更快的方法?这个函数处理 300 万的数据在我的 mac 上跑了 8 分钟…
    livc
        6
    livc  
    OP
       Sep 2, 2016
    @wickila 重大 bug 。。。把 sd 改成 11 月 8 日,输出了负值。。
    livc
        7
    livc  
    OP
       Sep 2, 2016
    @wickila 月份占位符应该小写。
    wickila
        8
    wickila  
       Sep 2, 2016
    @livc 多谢指正。效率的话,只能小幅度地优化 date2day 函数,不过提升的效率应该有限。看看有没有大神有其他办法。
    weimao
        9
    weimao  
       Apr 9, 2018
    td = _df['time']
    time = pd.to_datetime(td)
    start = pd.datetime(2014, 12, 8)
    day = time - start
    _df['time'] = day.dt.days
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