根據條件合並兩個數據框

Question

我想基於兩個數據幀之間的fact_date和scen的條件匹配來合並兩個數據幀，然后將altdate列添加到第二個數據幀。

第一個數據幀如下所示：

          fact_date   scen altdate
0        2008-08-18   -1  2008-08-25
1        2008-08-18    0  2008-08-18
2        2008-08-18    1  2008-08-15
3        2008-08-18    2  2008-08-14
4        2008-08-18    3  2008-08-13
5        2008-08-18    4  2008-08-12
6        2008-08-18    5  2008-08-11
7        2008-08-18    6  2008-08-08
8        2008-08-18    7  2008-08-07
9        2008-08-18    8  2008-08-06
...

第二個數據幀如下所示：

          fact_date  flag       scen  values
0        2008-08-18     0       -1   462456.29
1        2008-08-18     0        0  1119881.78
2        2008-08-18     0        1  1922320.74
3        2008-08-18     0        2  3559026.11
4        2008-08-18     0        3  3510447.61
5        2008-08-18     0        4  4873269.42
6        2008-08-18     0        5  5098557.55
7        2008-08-18     0        6  4610888.45
8        2008-08-18     0        7  4090821.69
9        2008-08-18     0        8  4219340.84
...

輸出應如下所示：

          fact_date  flag       scen  values     altdate
0        2008-08-18     0       -1   462456.29   2008-08-25
1        2008-08-18     0        0  1119881.78   2008-08-18
2        2008-08-18     0        1  1922320.74   2008-08-15
3        2008-08-18     0        2  3559026.11   2008-08-14
4        2008-08-18     0        3  3510447.61   2008-08-13
5        2008-08-18     0        4  4873269.42   2008-08-12
6        2008-08-18     0        5  5098557.55   2008-08-11
7        2008-08-18     0        6  4610888.45   2008-08-08
8        2008-08-18     0        7  4090821.69   2008-08-07
9        2008-08-18     0        8  4219340.84   2008-08-06
...

Answer 1

我不完全理解您的意思，但我認為您只想加入。 如果您使用的是熊貓，應該是這樣的：

df2 = df2.join(df1,on=['fact_date','scen'],how='left')

希望這可以幫助。

Answer 2

我會嘗試

df2.merge(df1, on=['fact_date', 'scen'])

哪個返回

    fact_date  flag  scen      values     altdate
0  2008-08-18     0    -1   462456.29  2008-08-25
1  2008-08-18     0     0  1119881.78  2008-08-18
2  2008-08-18     0     1  1922320.74  2008-08-15
3  2008-08-18     0     2  3559026.11  2008-08-14
4  2008-08-18     0     3  3510447.61  2008-08-13
5  2008-08-18     0     4  4873269.42  2008-08-12
6  2008-08-18     0     5  5098557.55  2008-08-11
7  2008-08-18     0     6  4610888.45  2008-08-08
8  2008-08-18     0     7  4090821.69  2008-08-07
9  2008-08-18     0     8  4219340.84  2008-08-06