01 NIS 2002-2011 Within Year Merge

<br>NIS 2002-2011 Within Year Merge - Each year of the NIS has a Core, Hospital and Severity file: File Level ID Core discharge KEY, HOSPID Hospital hospital HOSPID Severity discharge KEY, HOSPID 1. The 2 dischrage-level files will trimmed down to desired variables and then merged by KEY and saved into a temporary SAS dataset. 2. The hospital file will be trimmed and then merged into the core-severity and saved into a permanent SAS dataset with following notation: NIS_YYYY 3. Working directory cleared after every year since very large datasets.