Hey stata community,

I'm very new in using stata and have a question concerning the use of keeping same values.

My dataset looks like this:

Date | Molecule
01.01.1995 | Molecule 1
01.01.1995 | Molecule 1
10.05.1995 | Molecule 1
03.04.1998 | Molecule 2
03.04.1998 | Molecule 2
03.04.1998 | Molecule 2
05.07.1999 | Molecule 2
...

I only want to keep the first same values (date) per molecule, like this:

Date | Molecule
01.01.1995 | Molecule 1
01.01.1995 | Molecule 1
03.04.1998 | Molecule 2
03.04.1998 | Molecule 2
03.04.1998 | Molecule 2
...

How do I get there? The command sortby id: keep if _n==1 did not work as that only took the first of the observations.

Best regards,
Milena