For instance I have a data frame that includes 'datetime' as index and column 'a' as variable. I wanted to get information for each row, on which quantile they fall into, for example I want to use 4 level of categories like below, on specific date only.
So in the 'category' column, it will show that row 1 falls into first category on 2019-05-02 data.
datetime a category
2019-05-02 12:00 10 1
2019-05-02 13:00 10 1
2019-05-02 14:00 15 2
2019-05-02 15:00 20 4
2019-05-02 16:00 10 1
2019-05-02 17:00 15 3
2019-05-03 18:00 ...
Please don't mind the calculation. How do I define function to create the new column? Thanks!