Make dummy variable for categorical data, based on ID column with duplicate values in python

Question

I have the following pandas dataframe:

    ID    value
0   1     A
1   1     B
2   1     C
3   2     B
4   10    C
5   4     C
6   4     A

I want to make dummy variables for the values in the column 'value', for each value in the column 'ID'. So I want it this:

    ID    A    B    C
0   1     1    1    1
1   2     0    1    0
2   10    0    0    1
3   4     1    0    1

How can I do this in python?

`df.assign(dummy=1).pivot_table('dummy', 'ID', 'value', aggfunc='count', fill_value=0).clip(upper=1)` — Corralien, Mar 23 '22 at 07:14
@jezrael. You can reopen it if you think it's not just a pivot problem. — Corralien, Mar 23 '22 at 07:45

score 2 · Accepted Answer · answered Mar 23 '22 at 07:12

2

Use crosstab with limit counts to 1 by DataFrame.clip:

df1  = (pd.crosstab(df['ID'], df['value'])
          .clip(upper=1)
          .reset_index()
          .rename_axis(None, axis=1))
print (df1)
   ID  A  B  C
0   1  1  1  1
1   2  0  1  0
2   4  1  0  1
3  10  0  0  1

answered Mar 23 '22 at 07:12

jezrael

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Alternate: `pd.get_dummies(df['value']).groupby(df['ID']).max().reset_index()`, little less typing :p – Ch3steR Mar 23 '22 at 07:40

Make dummy variable for categorical data, based on ID column with duplicate values in python

1 Answers1