Dear all,
I need your valuable help and advice in the following please:
I have the following data , in which subject-id may have several visits dates and types (could be either screening , sampling or repeat sampling) and they may have different or same disease stage at each visit.
I want to answer the following question: how many subjects had disease stage 1 at their first visit ?
( so basically I want stata to only consider first visit only when calculating the proportion of certain disease category without having to drop the other observations)

Subject-id visit-date visit-name disease-stage
001 01/01/2017 screening 1
001 10/02/2018 sampling 1
001 01/01/2019 screening 1
001 05/06/2019 rep sampling 1
002 13/11/2016 screening 4
002 20/12/2016 sampling 4
003 09/04/206 screening 3
003 10/04/2016 sampling 4
004 11/05/2019 screening 2

TIA