如何根据data.frame中的两列将data.frame转换为矩阵 [英] How to convert data.frame into matrix based on two columns in data.frame

问题描述

我有一个数据框看起来像

I have a data frame looks like

    userId  movieId rating
0   12882   1      4.0
1   12882   32     3.5
2   12882   47     5.0
3   12882   50     5.0
4   12882   110    4.5

但是我想把它转换成一个矩阵，行名是userId，列名是movieId，值是评分.

But I want to convert it into a matrix which the rowname is userId, column name is movieId and the value is the rating.

         1    32      47
12882   4.0   3.5     5.0

我曾尝试使用 groupby，但在那之后，我不知道如何转换它.

I have try to use the groupby, but after that, I have no idea how to convert it.

test = Ratings[['userId','movieId','rating']]

test_group = test.groupby(['userId','movieId'],as_index=False,sort=False)

推荐答案

您可以使用 DataFrame.pivot 为此:

You can use DataFrame.pivot for this:

df_pivot = df.pivot(index='userId', columns='movieId', values='rating')

[出]

print(df_pivot)

movieId  1    32   47   50   110
userId                          
12882    4.0  3.5  5.0  5.0  4.5

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