Python共现选项卡

Question

我有一个数据集，如下所示：

df = pd.DataFrame([["1001","Category1"],["1001","Category1"],["1001","Category2"],["1002","Category1"],["1002","Category3"],["1001","Category3"],["1002", "Category2"],["1001", "Category3"],["1001","Category4"]], columns=['Id','Cat']))

     Id        Cat
0  1001  Category1
1  1001  Category1
2  1001  Category2
3  1002  Category1
4  1002  Category3
5  1001  Category3
6  1002  Category2
7  1003  Category3
8  1001  Category4

我想得到的是一种共现，就像下面这样，对于类别1中出现的每个ID，都有一个计数，这些ID在其他类别中出现的次数

df2 = pd.DataFrame([["nan","2","3","1"],["2","nan","2","1"],["3","2","nan","1"],["1","1","1","1"]],index = ['Category1','Category2','Category3'], columns=['Category1','Category2','Category3','Category4'])

          Category1 Category2 Category3 Category4
Category1         2         2         2         1
Category2         2         2         2         1
Category3         2         2         3         1
Category4         1         1         1         1

我在考虑使用.groupby()实现这一点，但我不确定如何像我的示例中那样获得每个类别

Answer 1

df['Cat'].value_counts()
"""
#Output:
Category1    4
Category3    3
Category2    2
Name: Cat, dtype: int64
"""

那能解决你的问题吗？你知道吗