I am attempting to make a column within my data frame that lists out the day number based on the count of each occurrence of another column. I want the counter to start again at 0 for every new group. Any help would be much appreciated!
I want it to look like this:
| Group | Date | Day |
| ------- | --------- | --- |
| a | 1/1/2022 | 0 |
| a | 1/2/2022 | 1 |
| a | 1/3/2022 | 2 |
| b | 1/1/2022 | 0 |
| b | 1/2/2022 | 1 |
| b | 1/3/2022 | 2 |
| c | 1/1/2022 | 0 |
| c | 1/2/2022 | 1 |
| c | 1/3/2022 | 2 |
>Solution :
Given the Group and Date column, this might be, what you are looking for:
df['Day'] = df.groupby('Group').cumcount()