Longitudinal Data and SAS

3   FIRST. and LAST. Temporary Variables

Introduction

How to Create FIRST. and LAST. Temporary Variables

Using More Than One BY Variable

A Simple Application Using FIRST. and LAST. Variables

Introduction

Let’s use the scenario of a clinical data set again, as a way of describing one common application of FIRST. and LAST. variables. You have a data set of patient visits to a clinic where each patient may have one or more visits (each visit being an observation). If you had an easy way to determine when you were reading the first observation (or the last observation) for each patient, you could use this information to count the number of visits for each patient or to determine if a given patient came in more than once for the same problem. FIRST. ...