我有一个相当复杂的问题。我需要在一组开始和结束日期内从数据框中选择行，然后对这些值求和并将它们放在新的数据帧中。
所以我从数据框df开始：
import random
dates = pd.date_range('20150101 020000',periods=1000)
df = pd.DataFrame({'_id': random.choice(range(0, 1000)),
'time_stamp': dates,
'value': random.choice(range(2,60))
})
并定义一些开始和结束日期：
import pandas as pd
start_date = ["2-13-16", "2-23-16", "3-17-16", "3-24-16", "3-26-16", "5-17-16", "5-25-16", "10-10-16", "10-18-16", "10-23-16", "10-31-16", "11-7-16", "11-14-16", "11-22-16", "1-23-17", "1-29-17", "2-06-17", "3-11-17", "3-23-17", "6-21-17", "6-28-17"]
end_date = pd.DatetimeIndex(start_date) + pd.DateOffset(7)
然后需要发生的是我需要创建一个新的数据框，其中weekly_sum汇总了value df列start_date列end_date和values。
因此，例如，新数据帧的第一行将返回{3}在2-13-16和2-20-16之间的总和。我想我会使用groupby.sum()或类似的东西。
可能看起来像这样：
id start_date end_date weekly_sum
65 2016-02-13 2016-02-20 100
非常感谢任何方向！
P.S。我知道我对random.choice的使用有点不稳定，所以如果你有更好的方法来生成随机数，我很乐意看到它！
答案 0 :(得分：2)
您可以使用
def get_dates(x):
# Select the df values between start and ending datetime.
n = df[(df['time_stamp']>x['start'])&(df['time_stamp']<x['end'])]
# Return first id and sum of values
return n['id'].values[0],n['value'].sum()
dates = pd.date_range('20150101 020000',periods=1000)
df = pd.DataFrame({'id': np.random.randint(0,1000,size=(1000,)),
'time_stamp': dates,
'value': np.random.randint(2,60,size=(1000,))
})
ndf = pd.DataFrame({'start':pd.to_datetime(start_date),'end':end_date})
#Unpack and assign values to id and value column
ndf[['id','value']] = ndf.apply(lambda x : get_dates(x),1).apply(pd.Series)
print(df.head(5))
id time_stamp value
0 770 2015-01-01 02:00:00 59
1 781 2015-01-02 02:00:00 32
2 761 2015-01-03 02:00:00 40
3 317 2015-01-04 02:00:00 16
4 538 2015-01-05 02:00:00 20
print(ndf.head(5))
end start id value
0 2016-02-20 2016-02-13 569 221
1 2016-03-01 2016-02-23 28 216
2 2016-03-24 2016-03-17 152 258
3 2016-03-31 2016-03-24 892 265
4 2016-04-02 2016-03-26 606 244
答案 1 :(得分：0)
您可以使用以下代码计算每周摘要。以下代码基于星期一。
import pandas as pd
import random
dates = pd.date_range('20150101 020000',periods=1000)
df = pd.DataFrame({'_id': random.choice(range(0, 1000)),
'time_stamp': dates,
'value': random.choice(range(2,60))
})
df['day_of_week'] = df['time_stamp'].dt.weekday_name
df['start'] = np.where(df["day_of_week"]=="Monday", 1, 0)
df['week'] = df["start"].cumsum()
# It is based on Monday.
df.head(20)
# Out[109]:
# _id time_stamp value day_of_week start week
# 0 396 2015-01-01 02:00:00 59 Thursday 0 0
# 1 396 2015-01-02 02:00:00 59 Friday 0 0
# 2 396 2015-01-03 02:00:00 59 Saturday 0 0
# 3 396 2015-01-04 02:00:00 59 Sunday 0 0
# 4 396 2015-01-05 02:00:00 59 Monday 1 1
# 5 396 2015-01-06 02:00:00 59 Tuesday 0 1
# 6 396 2015-01-07 02:00:00 59 Wednesday 0 1
# 7 396 2015-01-08 02:00:00 59 Thursday 0 1
# 8 396 2015-01-09 02:00:00 59 Friday 0 1
# 9 396 2015-01-10 02:00:00 59 Saturday 0 1
# 10 396 2015-01-11 02:00:00 59 Sunday 0 1
# 11 396 2015-01-12 02:00:00 59 Monday 1 2
# 12 396 2015-01-13 02:00:00 59 Tuesday 0 2
# 13 396 2015-01-14 02:00:00 59 Wednesday 0 2
# 14 396 2015-01-15 02:00:00 59 Thursday 0 2
# 15 396 2015-01-16 02:00:00 59 Friday 0 2
# 16 396 2015-01-17 02:00:00 59 Saturday 0 2
# 17 396 2015-01-18 02:00:00 59 Sunday 0 2
# 18 396 2015-01-19 02:00:00 59 Monday 1 3
# 19 396 2015-01-20 02:00:00 59 Tuesday 0 3
aggfunc = {"time_stamp": [np.min, np.max], "value": [np.sum]}
df2 = df.groupby("week", as_index=False).agg(aggfunc)
df2.columns = ["week", "start_date", "end_date", "weekly_sum"]
df2.iloc[58:61]
# Out[110]:
# week start_date end_date weekly_sum
# 58 58 2016-02-08 02:00:00 2016-02-14 02:00:00 413
# 59 59 2016-02-15 02:00:00 2016-02-21 02:00:00 413
# 60 60 2016-02-22 02:00:00 2016-02-28 02:00:00 413