将行类别转换为列

Question

I have an array of categories as follow.

mappingCategory = ["Animal", "Plant", "Animal", "Human", "Plant"]

Index	Category
0	Animal
1	Plant
2	Animal
3	Human
4	Plant

I want to convert the array into 2D array where the column is unique category (order by alphabet) and the rows show what category is in that row like this.

mappingCategory = [[1, 0, 0], [0, 0, 1], [1, 0, 0], [0, 1, 0], [0, 0, 1]]

Index	Animal	Human	Plant
0	1	0	0
1	0	0	1
2	1	0	0
3	0	1	0
4	0	0	1

I can build my own function to convert it, but is there any python build in function I could use?

Answer 1

You can use .str.get_dummies() , as follows:

If you have a dataframe column named Category , use:

df['Category'].str.get_dummies()

Or, if you do it directly from the array of categories:

mappingCategory = ["Animal", "Plant", "Animal", "Human", "Plant"]

pd.Series(mappingCategory).str.get_dummies()

Output:

   Animal  Human  Plant
0       1      0      0
1       0      0      1
2       1      0      0
3       0      1      0
4       0      0      1