根据条件、Python、Pandas 查找列中所有行的最小值 [英] Finding Minimums of all rows in a column, based on criteria, Python, Pandas

问题描述

你好 Stackoverflow 社区！

Hello Stackoverflow community!

我试图找到我的问题的答案，但没有成功.我基本上是在尝试从 excel 复制 MinIF 公式，但到目前为止，我一次只能为1"行做到这一点.这是我想要实现的目标的示例:

I have attemped to find an answer to my question but without success. I am basically trying to replicate the MinIF formula from excel, but so far I have only managed to do it for "1" row at a time. Here is an example of what I am trying to achieve:

请参阅附加链接

这个想法是，对于具有相同子组的所有产品，找到该组的最低价值/价格，并将其插入到它旁边的新列中.我希望我足够具体，我对 python 比较陌生，我什至不知道如何开始......

The idea is, that for all products with the same subgroup, the lowest value/price for that group is found, and inserted in a new column next to it. I hope i am being specific enough, I am relatively new to python, and I have literally no idea how to even start...

非常感谢帮助，谢谢.

推荐答案

我认为你需要 transform:

I think you need transform:

df['SubGroupLowestPrice'] = df.groupby('SubGroup')['Price'].transform('min')

示例:

df = pd.DataFrame({'A':[1,2,3,4,5,5],
                   'SubGroup':[1,5,5,6,6,6],
                   'Price':[7,8,9,10,2,3]})

print (df)
   A  Price  SubGroup
0  1      7         1
1  2      8         5
2  3      9         5
3  4     10         6
4  5      2         6
5  5      3         6

df['SubGroupLowestPrice'] = df.groupby('SubGroup')['Price'].transform('min')
print (df)
   A  Price  SubGroup  SubGroupLowestPrice
0  1      7         1                    7
1  2      8         5                    8
2  3      9         5                    8
3  4     10         6                    2
4  5      2         6                    2
5  5      3         6                    2

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