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[英]How do I add repeated month rows for every unique value in a pandas dataframe column?
[英]How do I copy rows in a pandas DataFrame and add an id column
我有一個數據框,如:
from pandas import DataFrame
import pandas as pd
x = DataFrame.from_dict({'farm' : ['A','B','A','B'],
'fruit':['apple','apple','pear','pear']})
如何使用id復制N
次,例如。 輸出(對於N=2
):
farm fruit sim
0 A apple 0
1 B apple 0
2 A pear 0
3 B pear 0
0 A apple 1
1 B apple 1
2 A pear 1
3 B pear 1
我嘗試了一種適用於R中數據幀的方法:
from numpy import arange
N = 2
sim_ids = DataFrame(arange(N))
pd.merge(left=x, right=sim_ids, how='left')
但是這會因錯誤MergeError: No common columns to perform merge on
而失敗MergeError: No common columns to perform merge on
。
謝謝。
不確定R在那里做什么,但這是一種做你想做的事情的方法:
In [150]: x
Out[150]:
farm fruit
0 A apple
1 B apple
2 A pear
3 B pear
[4 rows x 2 columns]
In [151]: N = 2
In [152]: DataFrame(tile(x, (N, 1)), columns=x.columns).join(DataFrame({'sims': repeat(arange(N), len(x))}))
Out[152]:
farm fruit sims
0 A apple 0
1 B apple 0
2 A pear 0
3 B pear 0
4 A apple 1
5 B apple 1
6 A pear 1
7 B pear 1
[8 rows x 3 columns]
In [153]: N = 3
In [154]: DataFrame(tile(x, (N, 1)), columns=x.columns).join(DataFrame({'sims': repeat(arange(N), len(x))}))
Out[154]:
farm fruit sims
0 A apple 0
1 B apple 0
2 A pear 0
3 B pear 0
4 A apple 1
5 B apple 1
6 A pear 1
7 B pear 1
8 A apple 2
9 B apple 2
10 A pear 2
11 B pear 2
[12 rows x 3 columns]
我可能會這樣做:
>>> df_new = pd.concat([df]*2)
>>> df_new["id"] = df_new.groupby(level=0).cumcount()
>>> df_new
farm fruit id
0 A apple 0
1 B apple 0
2 A pear 0
3 B pear 0
0 A apple 1
1 B apple 1
2 A pear 1
3 B pear 1
[8 rows x 3 columns]
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