Longitudinal Data and SAS

1   The RETAIN Statement

Introduction

Demonstrating a DATA Step with and without a RETAIN Statemen

Generating Sequential SUBJECT Numbers Using a Retained Variable

Using a SUM Statement to Create SUBJECT Numbers

Demonstrating That Variables Read with a SET Statement Are Retained

A Caution When Using a RETAIN Statement

Introduction

Suppose you have a SAS data set of clinical data. Each observation corresponds to a visit to the clinic and contains such information as a patient number, the date of the visit, and some information about the visit. It would be useful to compare information from one visit to another, for a given patient. How many days were there from the previous visit? Did this patient’s blood pressure go up or down? Questions such ...