Remove multiple observations based on one observation

[John O]

Dear all,

I am trying to remove multiple observations with the same patient id (ptid), if one of the observations for that patient fulfills a criteria (in this case age). I'm trying to google my way there, so far without any success. So basically a patient can be registered for multiple years, and if they are younger at any of these points (most likely the first observation), I want all of the observations for that patient to be removed...

Thank you so much for your help!
John

[Nick Cox]

Please show an example with a sample of your data, or data of similar form. dataex (SSC) can help mightily.

P.S.

1. Please re-register with a full real name, including family name, as requested.

2. one criterion, two criteria.