pandas 从一列开始合并,完全在其他列上? [英] pandas merge as of on one column, exactly on other columns?
问题描述
我正在尝试合并 2 个数据帧,在某些列上完全匹配,在其他列(通常是日期)上匹配 as_of
.这篇文章很好地描述了这个意图(我将复制粘贴下面的主要内容):
I am trying to merge 2 dataframes, with exact matching on some columns and as_of
matching on some other column (typically a date). The intention is very well described in this post (I'll copy paste the main content below):
上面的帖子已经回答了;只有它可以追溯到 2016 年,在引入 pandas.merge_asof
之前.我相信现在已经发布了一个更简单的答案.残酷的方法是将每组行的 as_of 合并为我想要完全合并的列的相同值.但是有没有更优雅的版本?
The post above was answered ; only it dates back from 2016, before the introduction of pandas.merge_asof
. I believe there can be an easier answer now that it's been released. Brutal approach would be to merge as_of for each group of rows with the same values for the cols on which I want to merge exactly on. But is there a more elegant version?
所需输入和输出的精确描述:
Precise description of desired input and outputs:
输入
df1 = pd.DataFrame({'index': ['a1','a2','a3','a4'], 'col1': ['1232','432','432','123'], 'col2': ['asd','dsa12','dsa12','asd2'], 'col3': ['1','2','2','3'], 'date': ['2010-01-23','2016-05-20','2010-06-20','2008-10-21'],}).set_index('index')
df1
Out[430]:
col1 col2 col3 date
index
a1 1232 asd 1 2010-01-23
a2 432 dsa12 2 2016-05-20
a3 432 dsa12 2 2010-06-20
a4 123 asd2 3 2008-10-21
df2 = pd.DataFrame({'index': ['b1','b2','b3','b4'], 'col1': ['132','432','432','123'], 'col2': ['asd','dsa12','dsa12','sd2'], 'col3': ['1','2','2','3'], 'date': ['2010-01-23','2016-05-23','2010-06-10','2008-10-21'],}).set_index('index')
df2
Out[434]:
col1 col2 col3 date b_col
index
b1 132 asd 1 2010-01-23 1
b2 432 dsa12 2 2016-05-23 2
b3 432 dsa12 2 2010-06-10 3
b4 123 sd2 3 2008-10-21 4
输出:
col1 col2 col3 date b_col
index
a2 432 dsa12 2 2016-05-20 2
a3 432 dsa12 2 2010-06-20 3
注意 1:我需要这样做的原因是我需要类似 groupby(...)[...].rolling(...).transform(...)代码> 的延迟似乎还不存在,除非我遗漏了什么?
NOTE 1: the reason why I need to do this is that I need something like groupby(...)[...].rolling(...).transform(...)
with latency which doesn't seem to exist yet, unless I am missing something?
注意 2:我想避免计算所有对,然后过滤,因为数据框可能会变得太大.
NOTE 2: I want to avoid computing all couples and then filtering as the dataframe may get too big.
推荐答案
我试图更接近您的问题.但是,我没有尝试 merge_asof 而是合并.我希望这种方法可以帮助您:
I have tried to get closer to your problem. However, I did not try merge_asof but merge. I hope this approach can help you:
import numpy as np
import pandas as pd
df1 = pd.DataFrame({'index': ['a1', 'a2', 'a3', 'a4'], 'col1': ['1232', '432', '432', '123'],
'col2': ['asd', 'dsa12', 'dsa12', 'asd2'], 'col3': ['1', '2', '2', '3'],
'date': ['2010-01-23', '2016-05-20', '2010-06-20', '2008-10-21'],
}).set_index('index')
df2 = pd.DataFrame({'index': ['b1', 'b2', 'b3', 'b4'], 'col1': ['132', '432', '432', '123'],
'col2': ['asd', 'dsa12', 'dsa12', 'sd2'], 'col3': ['1', '2', '2', '3'],
'date': ['2010-01-23', '2016-05-23', '2010-06-10', '2008-10-21'],
}).set_index('index')
columns = ['col1', 'col2', 'col3']
new_dic = pd.merge(df1, df2, on=columns, right_index=True).drop_duplicates(subset=['date_x']).drop(labels='date_y', axis=1)
print(new_dic)
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