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  Computing Differences between Observations

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

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

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

24.8  Problems

 

24.1  Introduction

You might encounter data sets with multiple observations per subject (or other groupings such as transactions on a single day or observations grouped in other ways). These data structures are sometimes ...