Fundamentals of programming in sas a case studies approach

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The correct bibliographic citation for this manual is as follows: Blum, James and Jonathan

Duggins. 2019. Fundamentals of Programming in SAS®: A Case Studies Approach. Cary, NC: SAS Institute Inc.

Fundamentals of Programming in SAS®: A Case Studies Approach

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Chapter 1: Introduction to SAS

1.1 Introduction

1.2 Learning Objectives

1.3 SAS Environments

1.3.1 The SAS Windowing Environment

1.3.2 SAS Studio and SAS University Edition

1.4 SAS Fundamentals

1.4.1 SAS Language Basics

1.4.2 SAS DATA and PROC Steps

1.4.3 SAS Libraries and Data Sets

1.4.4 The SAS Log

1.5 Output Delivery System

1.6 SAS Language Basics

1.6.1 SAS Language Structure

1.6.2 SAS Naming Conventions

1.7 Chapter Notes

1.8 Exercises

1.1 Introduction

This chapter introduces basic concepts about SAS that are necessary to use it effectively. This

chapter begins with an introduction to some of the available SAS environments and describes

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the basic functionality of each. Essentials of coding in SAS are also introduced through some

pre‐constructed sample programs. These programs rely on several data sets, some provided

with SAS, others are provided separately with the textbook, including those that form the basis

for the case study used throughout Chapters 2 through 7. Therefore, this chapter also

introduces SAS data sets and libraries. In addition, an introduction to debugging code is

included, which includes a discussion of the SAS log where notes, warnings, and error

messages are provided for any code submitted.

1.2 Learning Objectives

This chapter provides a basis for working in SAS, which is a necessary first step for successful

mastery of the material contained in the remainder of this book. In detail, it is expected upon

completion of this chapter that the following concepts are understood within the chosen SAS

environment:

Demonstrate the ability to open, edit, save, and submit a SAS program

Apply the LIBNAME statement to create a user‐defined library—including the BookData

library that contains all files for this text, downloadable from the Author Page

Demonstrate the ability to navigate through libraries and view data sets

Think critically about all messages SAS places in the log to determine their cause and

severity

Apply ODS statements to manage output and output destinations

Explain the basic rules and structure of the SAS language

Demonstrate the ability to apply a template to customize output

Use the concepts of this chapter to solve the problems in the wrap‐up activity. Additional

exercises and case‐studies are also available to test these concepts.

1.3 SAS Environments

Interacting with SAS is possible in a variety of environments, including SAS from the command

line, the SAS windowing environment, SAS Enterprise Guide, SAS Studio, and SAS University

Edition; with most of these being available on multiple operating systems. This chapter

introduces the SAS windowing environment, SAS Studio, and SAS University Edition on the

Microsoft Windows operating system and points out key differences between those SAS

environments. For further specifics on differences across SAS environments and operating

systems, consult the appropriate SAS Documentation. In nearly all examples in this book, code

is given outside of any specific environment and output is shown in generic RTF‐style tables or

standard image formats. Output may vary somewhat from the default styles across SAS

environments on various operating systems, and examples later in this chapter demonstrate

some of these differences. Later chapters give information about how to duplicate the table

styles.

1.3.1 The SAS Windowing Environment

The SAS windowing environment is shown in Figure 1.3.1 with three windows visible: Log,

Explorer, and Editor (commonly referred to as the Enhanced Program Editor). The Results and

Output windows are two other windows commonly available by default, but are typically

obfuscated by other windows at launch. When code that generates output is executed, these

windows (and possibly others) become relevant.

Figure 1.3.1: SAS Windowing Environment on Microsoft Windows

In the Microsoft Windows operating system, the menu and toolbars in the SAS windowing

environment have a similar look and feel compared to other programs running on Windows.

Exploring the menus reveals standard options under the File, Edit, and Help menus (such as

Open, Save, Clear, Find). The View, Tools, Solutions, and Window menus have specialized

options related to windows and utilities that are specific to SAS. The Run menu is dedicated to

submissions of SAS code, including submissions to a remote session. As is typical in most

applications, toolbar buttons in SAS provide quick access to common menu functions and vary

depending on which window is active in the session. Some menu and toolbar options are

reviewed below during the execution of the supplied sample code given in Program 1.3.1. This

sample code is available from the author web pages for this book.

Program 1.3.1: Demonstration Code

options ps=100 ls=90 number pageno=1 nodate;

data work.cars;

set sashelp.cars;

mpg_combo=0.6*mpg_city+0.4*mpg_highway;

select(type);

when(‘Sedan’,’Wagon’) typeB=’Sedan/Wagon’;

when(‘SUV’,’Truck’) typeB=’SUV/Truck’;

otherwise typeB=type;

end;

label mpg_combo=’Combined MPG’ typeB=’Simplified Type’;

run;

title ‘Combined MPG Means’;

proc sgplot data=work.cars;

hbar typeB / response=mpg_combo stat=mean limits=upper;

where typeB ne ‘Hybrid’;

run;

title ‘MPG Five­Number Summary’;

title2 ‘Across Types’;

proc means data=cars min q1 median q3 max maxdec=1;

class typeB;

var mpg:;

run;

After downloading the code to a known directory, there are multiple ways to navigate to and

open this code. Figure 1.3.2 shows two methods to open the file, each requiring the Editor

window to be active.

Figure 1.3.2: Methods for Opening SAS Code Files in the SAS Windowing Environment

Either of these choices launches a standard Microsoft Windows file selection window, which is

used to navigate to and select the file of interest. Upon successful selection of the code, it

appears in the Editor window, and is displayed with some color coding as shown in Figure 1.3.3

(assuming the Enhanced Program Editor is in use, the Program Editor window provides

different color coding). It is not important to understand the specific syntax or how the code

works at this point, for now it is used simply to provide an executable program to introduce

some SAS fundamentals.

Code submission can also occur in multiple ways, two of which are shown in Figure 1.3.3, again

each method requires the Editor window to be the active window in the session. If multiple

Editor windows are open, only code from the active window is submitted.

Figure 1.3.3: Submitting SAS Code in the SAS Windowing Environment

Typically, after any code submission the Results window activates and displays an index of links

to various entities produced by the program, including output tables. While not all SAS code

generates output, Program 1.3.1 does, and it may be routed to different destinations (and

possibly more than one destination simultaneously) depending on the version of SAS in use

and current option settings.

In SAS 9.4, the default settings route output to an HTML file which is displayed in the Results

Viewer, a viewing window internal to the SAS session. Previous versions of SAS rely on the

Output window for tables, an option which remains available for use in the SAS 9.4 windowing

environment, and other specialized destinations for graphics. Default output options can be

set by navigating to the Tools menu, selecting Options, followed by Preferences from that sub‐

menu, and choosing the Results tab in the window that appears, as shown in Figure 1.3.4.

Figure 1.3.4: Managing Output for Program Submissions

Among other options, Figure 1.3.4 shows the option for Create HTML checked and Create

Listing unchecked. For tables, the listing destination is the Output window, so when Create

Listing is checked, tables also appear in the Output window in what appears as a plain text

form. It is possible to check both boxes, and it is also possible to check neither, whichever is

preferred.

In the remainder of this book, output tables are shown in an RTF form embedded inside the

book text, outside of any SAS Results window. Appearance of output tables and graphs in the

book is similar to what is produced by a SAS session, but is not necessarily identical when

default session options are in place. Later in this chapter, the ability to use SAS code to control

delivery of output to each of these destinations is demonstrated, along with use of the listing

destination as an output destination for graphics files.

1.3.2 SAS Studio and SAS University Edition

SAS Studio and SAS University Edition (which are, for the remainder of this text, singularly

referred to as SAS University Edition) interface with SAS through a web browser. Typically, the

browser used is the default browser for the machine hosting the SAS University Edition

session, but this is not a requirement. Figure 1.3.5 shows a typical result of launching SAS

University Edition (in this case using the Firefox browser on Microsoft Windows), launching in

visual programmer mode by default. A closer match to the structure of the SAS windowing

environment is provided by selecting SAS Programmer from the toolbar as shown.

Figure 1.3.5: SAS University Edition

Opening a program is accomplished via the Open icon on the toolbar, as illustrated in Figure

1.3.6, and the opened code is displayed in a manner very similar to the that of the Enhanced

Program Editor display shown in Section 1.3.1.

Figure 1.3.6: Opening a Program in SAS University Edition

Though in a different position, the toolbar icon for submission is the same as in the SAS

windowing environment, and selecting it produces output in the Results tab as shown in Figure

1.3.7.

Figure 1.3.7: Execution of a Program in SAS University Edition

A few important differences to note in SAS University Edition: first, the output is displayed

starting at the top, rather than at the bottom of the page as in the SAS windowing

environment. Second, there is an additional tab for Output Data in this session. In Section

1.4.3, libraries, data sets, and navigation to each are discussed; however, SAS University

Edition also includes a special tab whenever a program generates new data sets, which aids in

directly viewing those results. Finally, note that the Code, Log, Results, and Output Data tabs

are contained within the Program 1.3.1 tab, and each program opened is given its own set of

tabs. In contrast, the SAS windowing environment supports multiple Editor windows in a single

session, but they all share a common Log window, Output window, and (under default

conditions) output HTML file. As discussed in other examples and in Chapter Notes 1 and 2 in

Section 1.7, submissions from any and all Editor windows in the SAS windowing environment

are cumulative in the Log and Output windows; therefore, managing results in each

environment is quite different.

1.4 SAS Fundamentals

To build an initial understanding of how to work with programs in SAS, Program 1.3.1 is used

repeatedly in this section to introduce various SAS language elements and concepts. For both

SAS windowing environment and SAS University Edition, the features of each environment and

navigation within them are discussed in conjunction with the language elements that relate to

them.

1.4.1 SAS Language Basics

Program 1.4.1 is a duplicate of Program 1.3.1 with certain elements noted numerically

throughout the code, followed by notes on the specific code in the indicated position.

Throughout this book, this style is used to detail important features found in sample code.

Program 1.4.1: Program 1.3.1, Revisited

options ps=100 ls=90 number pageno=1 nodate;

data work.cars;

set sashelp.cars;

MPG_Combo=0.6*mpg_city+0.4*mpg_highway;

select(type);

when(‘Sedan’,’Wagon’) TypeB=’Sedan/Wagon’;

when(‘SUV’,’Truck’) TypeB=’SUV/Truck’;

otherwise TypeB=type;

end;

label mpg_combo=’Combined MPG’ typeB=’Simplified Type’;

run;

title ‘Combined MPG Means’;

proc sgplot data=work.cars;

hbar typeB / response=mpg_combo stat=mean limits=upper;

where typeB ne ‘Hybrid’;

run;

title ‘MPG Five­Number Summary’;

title2 ‘Across Types’;

proc means data=work.cars min q1 median q3 max maxdec=1;

class typeB;

var mpg:;

run;

 SAS code is written in statements, each of which ends in a semicolon. The statements

indicated here (OPTIONS and TITLE) are examples of global statements. Global statements are

statements that take effect as soon as SAS compiles those statements. Typically, the effects

remain in place during the SAS session until another statement is submitted that alters those

effects.

 The SAS DATA step has a variety of uses; however, it is primarily a tool for creation or

manipulation of data sets. A DATA step is generally comprised of several statements forming a

block of code, ending with the RUN statement, the role of which is described in .

 Procedures in SAS are used for a variety of tasks and, like the DATA step, are generally

comprised of several statements. These are generically referred to as PROC steps.

 The PROC MEANS result includes the variables MPG_City, MPG_Highway, and MPG_Combo

even though none of these are explicitly written in the procedure code. The colon (:) at the end

of a variable name acts as a wildcard indicating that any variable name starting with the prefix

given is part of the designated set, this shortcut is known in SAS as a name prefix list. For other

types of variable lists, see Chapter Note 3 in Section 1.7.