Dear Statalist Users,

Although I went through many related discussions and explanations about my question, nothing helped me. I will be thankful for your suggestions in the following problem.
I am working with a Call Details Record (CDR) Dataset. In the data, for each caller id I observe the antenna used to make/receive call. I want to generate the variable for the number of times a certain antenna is used by a caller. What I am looking for is the following:

caller_id time antenna_id count_var
1 t_11 50 2
1 t_12 55 1
1 t_13 50 2

2 t_21 51 1
2 t_22 52 1
2 t_23 53 3
2 t_24 53 3
2 t_25 53 3

3 t_31 55 2
3 t_32 55 2
3 t_33 50 1
3 t_34 51 1
3 t_35 52 2
3 t_36 52 2
3 t_37 54 3
3 t_38 54 3
3 t_39 54 3
...

Thanks in advance for your cooperation. Bests.


S.