groupby counter of rows

Question

I am trying to create a new variable which counts how many times had been seen the same id over time.

Need to pass from this dataframe

   id     clae6  y         


        

Answer 1

By using cumcount

df.groupby('id').cumcount().add(1)
Out[1574]: 
0     1
1     2
2     3
3     4
4     5
5     6
6     1
7     2
8     3
9     4
10    5
11    1
12    2
13    3
14    4
dtype: int64

Answer 2

You can use rank

df['new'] = df.groupby('id').rank(method = 'first').astype(int)

    id  clae6   year    quarter new
0   1   475230.0    2007    1   1
1   1   475230.0    2007    2   2
2   1   475230.0    2007    3   3
3   1   475230.0    2007    4   4
4   1   475230.0    2008    1   5
5   1   475230.0    2008    2   6
6   2   475230.0    2007    1   1
7   2   475230.0    2007    2   2
8   2   475230.0    2007    3   3
9   2   475230.0    2007    4   4
10  2   475230.0    2008    1   5
11  3   475230.0    2010    1   1
12  3   475230.0    2010    2   2
13  3   475230.0    2010    3   3
14  3   475230.0    2010    4   4