get_dummies 和一起计数
问题描述
我有一个数据框,其中包含不同的案例"作为行,其中有一个 id 和一个类别:
I have a dataframe with different "cases" as rows, in which there's an id and a category:
df = DataFrame({ 'id':[1122,3344,5566,5566,3344,5566,1122,3344],
'category':['health','transport','energy','energy','transport','transport','transport','energy']})
category id
0 health 1122
1 transport 3344
2 energy 5566
3 energy 5566
4 transport 3344
5 transport 5566
6 transport 1122
7 energy 3344
我正在尝试找到一种既可以获取类别的虚拟变量并对其进行计数的好方法,所以通过上面的示例我会得到:
I'm trying to find a good way to both get dummies of the categories and also count them, so with the above example I would get this:
health transport energy
1122 1 1 0
3344 0 2 1
5566 0 1 2
有什么想法吗?
解决方案
你可以使用pivot_table() 方法:
In [71]: df.pivot_table(index='id', columns='category', aggfunc='size', fill_value=0)
Out[71]:
category energy health transport
id
1122 0 1 1
3344 1 0 2
5566 2 0 1
或:
In [76]: df.pivot_table(index='id', columns='category', aggfunc='size', fill_value=0).rename_axis(None, 1)
Out[76]:
energy health transport
id
1122 0 1 1
3344 1 0 2
5566 2 0 1
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