Learning SAS by Example

Chapter 24  Working with Multiple Observations per Subject

24.1  Introduction

24.2  Identifying the First or Last Observation in a Group

24.3  Counting the Number of Visits Using PROC FREQ

24.4  Counting the Number of Visits Using PROC MEANS

24.5  Computing Differences between Observations

24.6  Computing Differences between the First and Last Observation in a BY Group Using the LAG Function

24.7  Computing Differences between the First and Last Observation in a BY Group Using a RETAIN Statement

24.8  Using a Retained Variable to “Remember” a Previous Value

24.9  Problems

24.1  Introduction

You will encounter many data sets with multiple observations per subject (or other groupings such as transactions on a single day or observations grouped ...