pandas 熊猫按列值排名
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Pandas rank by column value
提问by Christopher Jenkins
I have a dataframe that has auction IDs and bid prices. The dataframe is sorted by auction id (ascending) and bid price (descending):
我有一个包含拍卖 ID 和出价的数据框。数据框按拍卖 ID（升序）和出价（降序）排序：
Auction_ID Bid_Price
123 9
123 7
123 6
123 2
124 3
124 2
124 1
125 1
I'd like to add a column called 'Auction_Rank' that ranks auction id's by bid prices:
我想添加一个名为“Auction_Rank”的列，按出价对拍卖 ID 进行排名：
Auction_ID Bid_Price Auction_Rank
123 9 1
123 7 2
123 6 3
123 2 4
124 3 1
124 2 2
124 1 3
125 1 1
回答by Zero
Here's one way to do it in Pandas-way
这是在 Pandas-way 中实现的一种方法
You could groupbyon Auction_IDand take rank()on Bid_Pricewith ascending=False
你可以groupby上Auction_ID，并采取rank()在Bid_Price与ascending=False
In [68]: df['Auction_Rank'] = df.groupby('Auction_ID')['Bid_Price'].rank(ascending=False)
In [69]: df
Out[69]:
Auction_ID Bid_Price Auction_Rank
0 123 9 1
1 123 7 2
2 123 6 3
3 123 2 4
4 124 3 1
5 124 2 2
6 124 1 3
7 125 1 1
