Contents

List of Programs

Preface

Acknowledgments

Chapter 1: The RETAIN Statement

• Introduction
• Demonstrating a DATA Step with and without a RETAIN Statement
• 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

Chapter 2: The LAG and DIF Functions

• Introduction
• Using the LAG Function to Compute Differences
• Demonstrating Some Related Functions: LAG2, LAG3, and So Forth
• Demonstrating the DIF Function

Chapter 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

Chapter 4: Flags and Counters

• Introduction
• Using a Flag Variable to Determine if a Particular Event Ever Occurred in Any One of Several Observations for Each Subject
• Counting the Number of Positive Outcomes for Each Patient

Chapter 5: Summarizing Data Using PROC MEANS and PROC FREQ

• Introduction
• Using PROC MEANS to Output Means to a Data Set
• Comparing CLASS and BY Statements with PROC MEANS
• Computing Other Descriptive Statistics
• Automatically Naming the Variables in the Output Data Set
• Demonstrating an Alternative Way to Select Specific Descriptive Statistics for Selected Variables
• Adding Additional Variables to the Summary Data Set Using an ID Statement
• Specifying More Than One CLASS Variable
• Selecting Multi-Way Breakdowns Using the TYPES Statement
• Using the PROC MEANS CHARTYPE Option to Simplify the _TYPE_ Interpretation
• Comparing PROC MEANS and PROC FREQ for Creating an Output Data Set Containing Counts
• Counting Frequencies for a Two-Way Table

Chapter 6: Using PROC SQL with Longitudinal Data

• Introduction
• Creating a Demonstration Data Set
• A Simple SQL Query
• Using PROC SQL to Count Observations within a BY Group
• Demonstrating a HAVING Clause
• Using PROC SQL to Create a Macro Variable
• Using a Summary Function to Compute Group Means

Chapter 7: Restructuring SAS Data Sets Using Arrays

• Introduction
• Creating a New Data Set with Several Observations per Subject from a Data Set with One Observations per Subject
• Another Example of Creating Multiple Observations from a Single Observation
• Going from One Observation per Subject to Many Observations per Subject Using Multidimensional Arrays
• Demonstrating the Use of a Multidimensional Array
• An Alternative Program
• Another Example of a Multidimensional Array

Chapter 8: Restructuring SAS Data Sets Using PROC TRANSPOSE

• Introduction
• Going from One Observation to Several Observations
• Another Example of Creating Multiple Observations from a Single Observation
• Going from One Observation per Subject to Many Observations
• Creating a Data with One Observation per Subject from a Data Set

Chapter 9: Study One: Operations on a Clinical Database

• Introduction
• Description of the Clinical Data Set
• Selecting the First or Last Visit for Each Patient
• Computing Differences between the First and Last Visits
• Another Method of Computing Differences between the First and Last Visits
• Computing Differences between Every Visit
• Counting the Number of Visits for Each Patient (DATA Step Approach)
• Counting the Number of Visits for Each Patient (PROC FREQ)
• Counting the Number of Visits for Each Patient (PROC MEANS)
• Counting the Number of Visits for Each Patient (PROC SQL)
• Selecting All Patients with n Visits (DATA Step Approach)
• Selecting All Patients with Two Visits (Using PROC SQL)
• Selecting All Patients with Two Visits (Using SQL in One Step)
• Using PROC SQL to Create a Macro Variable
• Computing Summary Statistics for Each Patient (Using PROC MEANS)
• Computing Summary Statistics for Each Patient (Using PROC SQL)
• Adding a Value from the First Visit to Each Subsequent Visit
• Looking Ahead: Making a Decision about the Current Observation Based on Information in the Next Observation
• Using Flags to Ascertain Vitamin Use
• Using PROC FREQ to Ascertain Vitamin Use
• Counting the Number of Routine Visits for Each Patient

Chapter 10: Study Two: Operations on Daily Weather Data and Ozone Levels

• Introduction
• The OZONE Data Set
• Computing Weekly Averages
• Using the MOD Function to Group Data Values
• Computing a Moving Average for a Single Variable

Chapter 11: Study Three: Study Three: Producing Summary Reports on a Library Data Set

• Introduction
• Computing the Number of Books per Patron Visit and by Library
• Computing the Number of Patrons by Day of Week and Library
• Generating a Table of LC Categories by Age Group and Overall

Chapter 12: Useful Macros

• Introduction
• Listing All or Part of a Data Set
• Computing Differences between Successive Observations
• Computing Differences between the First and Last Observations per Subject
• Computing a Moving Average
• Computing Cell Means and Counts
• Couting the Number of Observations per Subject

Appendix: List of Data Files and SAS Data Sets

• The TEST_SCORES Data Set
• The CLINICAL Data Set
• The CLIN_FIRST Data Set
• The OZONE Data Set
• The LIBRARY Data Set

Index