[英]Python: How to find most frequent combination of elements?
A machine provides fault codes which are provided in a pandas dataframe.机器提供熊猫数据帧中提供的故障代码。 id
identifies the machine, code
is the fault code: id
标识机器, code
为故障代码:
df = pd.DataFrame({
"id": [1,1,1,1,1,2,2,2,2,3,3,3,3,3,3,4],
"code": [1,2,5,8,9,2,3,5,6,1,2,3,4,5,6,7],
})
Reading example: Machine 1 generated 5 codes: 1,2,5,8 and 9.阅读示例:机器 1 生成了 5 个代码:1、2、5、8 和 9。
I want to find out which code combinations are most frequent across all machines.我想找出所有机器上最常见的代码组合。 The result for the example would be something like [2]
(3x), [2,5]
(3x), [3,5]
(2x) and so on.该示例的结果将类似于[2]
(3x)、 [2,5]
(3x)、 [3,5]
(2x) 等。
How can I achive this?我怎样才能做到这一点? As there is a lot of data, I'm looking for a efficient solution.由于有大量数据,我正在寻找有效的解决方案。
Here are two other ways to represent the data (in case that makes the calculation easier):以下是表示数据的另外两种方法(以防计算更容易):
pd.crosstab(df.id, df.code)
df.groupby("id")["code"].apply(list)
Use custom function all_subsets
, then flatten values by Series.explode
and last use Series.value_counts
:使用自定义函数all_subsets
,然后按Series.explode
压平值,最后使用Series.value_counts
:
from itertools import chain, combinations
#https://stackoverflow.com/a/5898031
#only converted to list and removed empty tuples by range(1,...
def all_subsets(ss):
return list(chain(*map(lambda x: combinations(ss, x), range(1, len(ss)+1))))
s = df.groupby('id')['code'].apply(all_subsets).explode().value_counts()
print (s)
(2,) 3
(2, 5) 3
(5,) 3
(1, 2) 2
(3, 6) 2
..
(1, 5, 8) 1
(9,) 1
(1, 3, 4, 6) 1
(5, 8, 9) 1
(4, 6) 1
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