Consolidate records from multiple variables

[Oversea_rep]

Hi,

I have a dataset with multiple variables for different cohorts. The dataset contains date of birth variable, sex, race and vaccine dates from 3 follow-up periods and therefore three cohorts. I would like to consolidate the demographic variables for all subjects from the different cohorts in the dataset into one single demographic variable for sex, gender, dob, vaccine date, etc.

Note: some subjects belong to more than one cohort. They were re-enrolled for follow-up.

Edit: I added the remaining variables to the table. Race/ethnicity and gender are categorical variables.

Example of the dataset:

Studyid	cohort1_dob	cohort2_dob	cohort3_dob	Race/ethnicity cohort1	Race/ethnicity cohort 2	Race/ethnicity cohort 3	Gender cohort 1	Gender cohort 2	Gender cohort 3	cohort1_vaxdate	cohort2_vaxdate	cohort3_vaxdate
001	.	.	12/31/1990	.	.	1	.	.	5	.	.	14/06/2005
002	10/05/1998	.	.	1	.	.	1	.	.	15/06/2004	.	.
003	02/01/1994	.	02/01/1994	2	.	2	3	.	3	23/07/2009	.	16/03/2021
004	03/04/1989	03/04/1989	.	1	1	.	1	1	.	16/05/2006	08/08/2013
005	.	04/05/2009	.	.	2	.	.	1	.		14/04/2008
006	05/07/2008	.	05/07/2008	1	.	1	3	.	3	04/12/2012	.	17/06/2017

[andreas_lds]

I don't see any of the variables you mention in the table you have posted, so please post the data in usable form and include all variables that are in the dataset. Merging variables is almost always a bad idea, because it will be more difficult to use the new variable to filter the data.