I have the following panel data of one individual in the study. WHO stage was recorded multiple times, but I only want to identify the first record of WHO stage, make a new variable for this first WHO stage and copy that stage to all observations of the panel data for the individual. The data looks as follows:

Code:
* Example generated by -dataex-. For more info, type help dataex
clear
input double id byte who_stage float visit_lab_date
829 .     .
829 4 20898
829 .     .
829 .     .
829 .     .
829 . 20919
829 .     .
829 .     .
829 .     .
829 .     .
829 3 20954
829 .     .
829 .     .
829 . 21014
829 .     .
829 .     .
829 . 21133
829 .     .
829 .     .
829 .     .
829 1 21336
829 .     .
829 1 21336
829 .     .
829 . 21417
829 . 21417
829 . 21417
829 . 21417
829 . 21417
829 1 21427
829 .     .
829 .     .
829 . 21427
829 .     .
829 .     .
829 .     .
829 . 21623
829 .     .
829 1 21623
829 . 21735
829 .     .
829 1 21735
829 .     .
829 .     .
829 1 21882
829 .     .
829 1 21882
829 .     .
829 . 21910
829 .     .
829 .     .
829 . 21939
829 .     .
829 . 21970
829 . 21999
829 . 21999
829 . 21999
829 . 21999
829 . 21999
829 1 22092
end
format %td visit_lab_date
Thanks in advance for all your time and help!