I have a dataset that looks like this: Patient_ID Age Obs_date Obs_value treatment 1 19 03/04/2020 A 1 . 12/09/2018 A 1 . 01/05/2019 . 2 . 12/22/2021 B 2 35 06/12/2018 A 2 . 04/12/2014 . 2 . 09/17/2020 . 2 . 08/28/2015 . 2 . 09/09/2021 C 2 . 03/31/2000 . 3 16 02/04/2017 A 3 . 09/12/2018 A 3 . 10/10/2020 A 4 44 05/22/2016 B 5 28 05/08/2016 B 5 . 09/05/2016 . 5 . 01/25/2017 . 5 . 01/09/2014 . 5 . 12/12/2014 A 5 . 07/18/2016 A 5 . 09/12/2012 . 5 . 06/07/2013 A 5 . 01/30/2017 C I am trying to create a dataset with patients who: Aged≥18 years old Have Obs_date after from 03/01/2017 onwards The new dataset should exclude patient_ID 3 (below 18 years old) and patient_IDs 4&5 (all Obs_dates are prior to 03/01/2017) I tried the following: data want; set have; if age =>18; if '1mar2017'd <= obs_date; run; The output successfully deleted patient_IDs 3, 4, and 5; however, for patient_IDs 1&2, only one observation is kept for each. I’d like to keep all observations for patient_IDs 1&2 (screenshot below) I'm looking for an output like the following: Patient_ID Age Obs_date Obs_value treatment 1 19 03/04/2020 A 1 . 12/09/2018 A 1 . 01/05/2019 . 2 . 12/22/2021 B 2 35 06/12/2018 A 2 . 04/12/2014 . 2 . 09/17/2020 . 2 . 08/28/2015 . 2 . 09/09/2021 C 2 . 03/31/2000 .
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