How to compare dates with the next row and exclude rows based on the criteria?

[mrafael03]

Hello,

I'll start by providing the requirement:

• Blue highlighted dates are the expected results
• DAYS_DIFF = 1st DISCH_DT - NEXT ADMIT_DT

[mrafael03]

CONTINUATION...

1. If the discharge is followed by readmission or direct transfer to an acute inpatient care setting within 30-day follow-up period, count only the last discharge.

e.g.

ID     ADMIT_DT   DISCH_DT   DAYS_DIFF

011    1/10/2018       1/13/2018         16      <<< "readmission within 30 days - only include last discharge"

011    1/29/2018       2/28/2018

022    2/13/2018        2/17/2018        55      <<< "readmission >30 days"
022    4/13/2018        4/25/2018

2. For member with same admission date, but different discharge dates; use the last discharge date.

e.g.

ID    ADMIT_DT   DISCH_DT 

033   5/11/2018     5/12/2018
033   5/11/2018     5/17/2018   

3. For member with same discharge date, but different admit date; use the first admit date.

e.g.

ID    ADMIT_DT   DISCH_DT 

033  6/11/2018     6/17/2018
033  6/13/2018     6/17/2018

4. For member with the same 1st discharge date and next admit date, count the 1st admit date and next discharge date.

e.g.

ID     ADMIT_DT   DISCH_DT  DAYS_DIFF

033  08/11/2018    08/17/2018        0
033  08/17/2018     08/23/2018

I would like to loop through the dataset by using RETAIN STATEMENT. See the attachment for my SAS codes. I'm still a newbie in SAS and trying to figure out on how to retain/remove rows  based on the criteria. Any help would be greatly appreciated. Thank you!