[英]Merge pandas dataframe on time and another column
我有兩個熊貓數據框,試圖將它們組合成一個數據框。 這是我設置它們的方法:
a = {'date':['1/1/2015 00:00','1/1/2015 00:15','1/1/2015 00:30'], 'num':[1,2,3]}
b = {'date':['1/1/2015 01:15','1/1/2015 01:30','1/1/2015 01:45'], 'num':[4,5,6]}
dfa = pd.DataFrame(a)
dfb = pd.DataFrame(b)
dfa['date'] = dfa['date'].apply(pd.to_datetime)
dfb['date'] = dfb['date'].apply(pd.to_datetime)
然后,我從每個時間戳中找到earliest
和latest
時間戳,並創建一個僅以date
序列開頭的新數據框:
earliest = min(dfa['date'].min(), dfb['date'].min())
latest = max(dfa['date'].max(), dfb['date'].max())
date_range = pd.date_range(earliest, latest, freq='15min')
dfd = pd.DataFrame({'date':date_range})
然后,我想將它們全部合並到一個以dfd
為基礎的數據幀中,因為它將包含所有適當的時間戳。 所以我合並了dfd
和dfa
,一切都很好:
dfd = pd.merge(dfd, dfa, how = 'outer', on = 'date')
但是,當我將其與dfb
合並時, date
序列變得很混亂,我不知道為什么。
dfd = pd.merge(dfd, dfb, how = 'outer', on = ['date','num'])
...收益率:
date num
0 2015-01-01 00:00:00 1.0
1 2015-01-01 00:15:00 2.0
2 2015-01-01 00:30:00 3.0
3 2015-01-01 00:45:00 NaN
4 2015-01-01 01:00:00 NaN
5 2015-01-01 01:15:00 NaN
6 2015-01-01 01:30:00 NaN
7 2015-01-01 01:45:00 NaN
8 2015-01-01 01:15:00 4.0
9 2015-01-01 01:30:00 5.0
10 2015-01-01 01:45:00 6.0
我希望4.0
可以填充2015-01-01 01:15:00
時間段等,而不創建新行。
或者,如果我嘗試:
dfd = pd.merge(dfd, dfb, how = 'outer', on = 'date')
我得到:
date num_x num_y
0 2015-01-01 00:00:00 1.0 NaN
1 2015-01-01 00:15:00 2.0 NaN
2 2015-01-01 00:30:00 3.0 NaN
3 2015-01-01 00:45:00 NaN NaN
4 2015-01-01 01:00:00 NaN NaN
5 2015-01-01 01:15:00 NaN 4.0
6 2015-01-01 01:30:00 NaN 5.0
7 2015-01-01 01:45:00 NaN 6.0
這也不是我想要的(只想要一個num
列)。 任何幫助,將不勝感激。
dfa.set_index('date').combine_first(dfb.set_index('date')) \
.asfreq('15T').reset_index()
date num
0 2015-01-01 00:00:00 1.0000
1 2015-01-01 00:15:00 2.00
2 2015-01-01 00:30:00 3.00
3 2015-01-01 00:45:00 nan
4 2015-01-01 01:00:00 nan
5 2015-01-01 01:15:00 4.00
6 2015-01-01 01:30:00 5.00
7 2015-01-01 01:45:00 6.00
另一個解決方案
dfa.append(dfb).set_index('date').asfreq('15T').reset_index()
首先合並dfa和dfb:
d = pd.merge(dfa, dfb, on=['date','num'], how='outer')
然后將結果與定義的dfd合並:
result = pd.merge(d, dfd, on='date', how='outer')
print result.sort('date')
輸出:
date num
0 2015-01-01 00:00:00 1.0
1 2015-01-01 00:15:00 2.0
2 2015-01-01 00:30:00 3.0
6 2015-01-01 00:45:00 NaN
7 2015-01-01 01:00:00 NaN
3 2015-01-01 01:15:00 4.0
4 2015-01-01 01:30:00 5.0
5 2015-01-01 01:45:00 6.0
這有效:
a = {'date':['1/1/2015 00:00','1/1/2015 00:15','1/1/2015 00:30'], 'num':[1,2,3]}
b = {'date':['1/1/2015 01:15','1/1/2015 01:30','1/1/2015 01:45'], 'num':[4,5,6]}
dfa = pd.DataFrame(a)
dfb = pd.DataFrame(b)
dfa['date'] = dfa['date'].apply(pd.to_datetime)
dfb['date'] = dfb['date'].apply(pd.to_datetime)
earliest = min(dfa['date'].min(), dfb['date'].min())
latest = max(dfa['date'].max(), dfb['date'].max())
date_range = pd.date_range(earliest, latest, freq='15min')
dfd = pd.DataFrame({'date':date_range})
df_dates = pd.merge(dfa, dfb, how = 'outer')
df_final = pd.merge(dfd, df_dates, how = 'outer')
df_final
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