To program effectively using SAS, you need to understand basic concepts about SAS programs and the SAS files that they process. In particular, you need to be familiar with SAS data sets.
In this chapter, you'll examine a simple SAS program and see how it works. You'll learn details about SAS data sets (which are files that contain data that is logically arranged in a form that SAS can understand). You'll see how SAS data sets are stored temporarily or permanently in SAS libraries. Finally, you'll learn how to use SAS windows to manage your SAS session and to process SAS programs.
You can use SAS programs to access, manage, analyze, or present your data. Let's begin by looking at a simple SAS program. This program creates a new SAS data set from an existing SAS data set and then prints a listing of the new data set. A SAS data set is a data file that is formatted in a way that SAS can understand.
data clinic.admit2; set clinic.admit; run; proc print data=clinic.admit2; run;
Let's see how this program works.
Our sample SAS program contains two steps: a DATA step and a PROC step.
data clinic.admit2 set clinic.admit; run; proc print data=clinic.admit2; run;
These two types of steps, alone or combined, form most SAS programs.
DATA steps typically create or modify SAS data sets. They can also be used to produce custom-designed reports. For example, you can use DATA steps to
put your data into a SAS data set
compute values
check for and correct errors in your data
produce new SAS data sets by subsetting, merging, and updating existing data sets.
PROC (procedure) steps are pre-written routines that enable you to analyze and process the data in a SAS data set and to present the data in the form of a report. They sometimes create new SAS data sets that contain the results of the procedure. PROC steps can list, sort, and summarize data. For example, you can use PROC steps to
create a report that lists the data
produce descriptive statistics
create a summary report
produce plots and charts.
Next let's look at the individual statements in our sample program. SAS programs consist of SAS statements. A SAS statement has two important characteristics:
It usually begins with a SAS keyword.
It always ends with a semicolon.
As you've seen, a DATA step begins with a DATA statement, which begins with the keyword DATA. A PROC step begins with a PROC statement, which begins with the keyword PROC. Our sample program contains the following statements:
Statements | Sample Program Code |
|---|---|
 |
data clinic.admit2; |
 |
set clinic.admit; |
 |
run; |
 |
proc print data=clinic.admit2; |
 |
run; |
SAS statements are free-format. This means that
they can begin and end anywhere on a line
one statement can continue over several lines
several statements can be on a line.
Blanks or special characters separate words in a SAS statement.
You've examined the general structure of our sample program. But what happens when you run the program?
When you submit a SAS program, SAS begins reading the statements and checking them for errors.
DATA and PROC statements signal the beginning of a new step. When SAS encounters a subsequent DATA, PROC, or RUN statement (for DATA steps and most procedures) or a QUIT statement (for some procedures), SAS stops reading statements and executes the previous step in the program. In our sample program, each step ends with a RUN statement.
data clinic.admit2;
set clinic.admit;
run;
proc print data=clinic.admit2;
run;Each time a step is executed, SAS generates a log of the processing activities and the results of the processing. The SAS log collects messages about the processing of SAS programs and about any errors that occur.
When SAS processes our sample program, you see the log messages shown below. Notice that you get separate sets of messages for each step in the program.
Suppose you submit the sample program below:
data clinic.admit2;
set clinic.admit;
run;
proc print data=clinic.admit2;
run;When the program is processed, it
creates the SAS data set Clinic.Admit2 in the DATA step. The DATA step produces messages in the SAS log, but it does not create a report or other output.
creates the following listing report of the SAS data set Clinic.Admit2:
You've seen the results of submitting our sample program. For other SAS programs, the results of processing might vary:
Some SAS programs open an interactive window (a window that you can use to directly modify data), such as the REPORT window.
proc report data=clinic.admit; columns id name sex age actlevel; label name='Name' sex='Sex' age='Age' actlevel='ActLevel'; run;
SAS programs often invoke procedures that create output in the form of a report, as is the case with the TABULATE procedure:
Other SAS programs perform tasks such as sorting and managing data, which have no visible results except for messages in the log. (All SAS programs produce log messages, but some SAS programs produce only log messages.)
proc copy in=clinic out=work; select admit; run;
You've learned about SAS programs and SAS data sets. Now let's look at SAS libraries to see how SAS data sets and other SAS files are organized and stored.
Every SAS file is stored in a SAS library, which is a collection of SAS files. A SAS data library is the highest level of organization for information within SAS.
SAS libraries have different implementations depending on your operating environment, but a library generally corresponds to the level of organization that your host operating system uses to access and store files. In some operating environments, a library is a physical collection of files. In others, the files are only logically related.
For example, in the Windows and UNIX environments, a library is typically a group of SAS files in the same folder or directory.
The table below summarizes the implementation of SAS libraries in various operating environments.
In this environment… | A SAS library is… |
|---|---|
Windows, UNIX, OpenVMS, OS/2 (directory based-systems) | a group of SAS files that are stored in the same directory. Other files can be stored in the directory, but only the files that have SAS file extensions are recognized as part of the SAS library. |
| |
CMS | a group of SAS files that have the same file type. |
z/OS (OS/390) | a specially formatted host data set in which only SAS files are stored. |
To reference a permanent SAS data set in your SAS programs, you use a two-level name:
libref.filenameIn the two-level name, libref is the name of the SAS data library that contains the file, and filename is the name of the file itself. A period separates the libref and filename.
For example, in our sample program, Clinic.Admit is the two-level name for the SAS data set Admit, which is stored in the library named Clinic.
To reference temporary SAS files, you can specify the default libref Work, a period, and the filename. For example, the two-level name Work.Test references the SAS data set named Test that is stored in the temporary SAS library Work.
Alternatively, you can use a one-level name (the filename only) to reference a file in a temporary SAS library. When you specify a one-level name, the default libref Work is assumed. For example, the one-level name Test also references the SAS data set named Test that is stored in the temporary SAS library Work.
You can see that Clinic.Admit and Clinic.Admit2 are permanent SAS data sets because the library name is Clinic, not Work.
So referencing a SAS file in any library except Work indicates that the SAS file is stored permanently. For example, when our sample program creates Clinic.Admit2, it stores the new Admit2 data set permanently in the SAS library Clinic.
SAS data set names
can be 1 to 32 characters long
must begin with a letter (A-Z, either uppercase or lowercase) or an underscore (_)
can continue with any combination of numbers, letters, or underscores.
These are examples of valid data set names:
Payroll
LABDATA1995_1997
_EstimatedTaxPayments3
So far, you've seen the components and characteristics of SAS programs, including how they reference SAS data sets. Data sets are one type of SAS file. There are other types of SAS files (such as catalogs), but this chapter focuses on SAS data sets. For many procedures and for some DATA step statements, data must be in the form of a SAS data set to be processed. Now let's take a closer look at SAS data sets.
As you saw in our sample program, for many of the data processing tasks that you perform with SAS, you
access data in the form of a SAS data set
analyze, manage, or present the data.
Conceptually, a SAS data set is a file that consists of two parts: a descriptor portion and a data portion. Sometimes a SAS data set also points to one or more indexes, which enable SAS to locate records in the data set more efficiently. (The data sets that you work with in this chapter do not contain indexes.)
The descriptor portion of a SAS data set contains information about the data set, including
the name of the data set
the date and time that the data set was created
the number of observations
the number of variables.
Let's look at another SAS data set. The table below lists part of the descriptor portion of the data set Clinic.Insure, which contains insurance information for patients who are admitted to a wellness clinic. (It's a good idea to give your data set a name that is descriptive of the contents.)
Data Set Name: | CLINIC.INSURE |
Member Type: | DATA |
Engine: | V8 |
Created: | 10:05 Tuesday, March 30, 1999 |
Observations: | 12 |
Variables: | 7 |
Indexes: | 0 |
Observation Length: | 64 |
The data portion of a SAS data set is a collection of data values that are arranged in a rectangular table. In the example below, the name Jones is a data value, the weight 158.3 is a data value, and so on.
Rows (called observations) in the data set are collections of data values that usually relate to a single object. The values Jones, M, 48, and 128.6 comprise a single observation in the data set shown below.
This data set has four observations, each containing information about an individual. A SAS data set can store any number of observations.
Columns (called variables) in the data set are collections of values that describe a particular characteristic. The values Jones, Laverne, Jaffe, and Wilson comprise the variable Name in the data set shown below.
This data set contains four variables for each observation: Name, Sex, Age, and Weight. A SAS data set can store thousands of variables.
The rectangular arrangement of rows and columns in a SAS data set implies that every variable must exist for each observation. If a data value is unknown for a particular observation, a missing value is recorded in the SAS data set.
In addition to general information about the data set, the descriptor portion contains information about the attributes of each variable in the data set. The attribute information includes the variable's name, type, length, format, informat, and label.
When you write SAS programs, it's important to understand the attributes of the variables that you use. For example, you might need to combine SAS data sets that contain same-named variables. In this case, the variables must be the same type (character or numeric).
The following is a partial listing of the attribute information in the descriptor portion of the SAS data set Clinic.Insure. First, let's look at the name, type, and length variable attributes.
Variable | Type | Length | Format | Informat | Label |
|---|---|---|---|---|---|
Policy | Num | 8 | Policy Number | ||
Total | Num | 8 | DOLLAR8.2 | COMMA10. | Total Balance |
Name | Char | 20 | Patient Name |
Each variable has a name that conforms to SAS naming conventions. Variable names follow exactly the same rules as SAS data set names. Like data set names, variable names
can be 1 to 32 characters long
must begin with a letter (A-Z, either uppercase or lowercase) or an underscore (_)
can continue with any combination of numbers, letters, or underscores.
Variable | Type | Length | Format | Informat | Label |
|---|---|---|---|---|---|
Policy | Num | 8 | Policy Number | ||
Total | Num | 8 | DOLLAR8.2 | COMMA10. | Total Balance |
Name | Char | 20 | Patient Name |
A variable's type is either character or numeric.
Character variables, such as Name (shown below), can contain any values.
Numeric variables, such as Policy and Total (shown below), can contain only numeric values (the digits 0 through 9, +, -, ., and E for scientific notation).
Variable | Type | Length | Format | Informat | Label |
|---|---|---|---|---|---|
Policy | Num | 8 | Policy Number | ||
Total | Num | 8 | DOLLAR8.2 | COMMA10. | Total Balance |
Name | Char | 20 | Patient Name |
A variable's type determines how missing values for a variable are displayed. In the following data set, Name and Sex are character variables, and Age and Weight are numeric variables.
For character variables such as Name, a blank represents a missing value.
For numeric variables such as Age, a period represents a missing value.
A variable's length (the number of bytes used to store it) is related to its type.
Character variables can be up to 32,767 bytes long. In the example below, Name has a length of 20 characters and uses 20 bytes of storage.
All numeric variables have a default length of 8. Numeric values (no matter how many digits they contain) are stored as floating-point numbers in 8 bytes of storage, unless you specify a different length.
Variable | Type | Length | Format | Informat | Label |
|---|---|---|---|---|---|
Policy | Num | 8 | Policy Number | ||
Total | Num | 8 | DOLLAR8.2 | COMMA10. | Total Balance |
Name | Char | 20 | Patient Name |
You've seen that each SAS variable has a name, type, and length. In addition, you can optionally define format, informat, and label attributes for variables. Let's look briefly at these optional attributes—you'll learn more about them in later chapters as you need to use them.
Formats are variable attributes that affect the way data values are written. SAS software offers a variety of character, numeric, and date and time formats. You can also create and store your own formats. To write values out using a particular form, you select the appropriate format.
For example, to display the value 1234 as $1234.00 in a report, you can use the DOLLAR8.2 format, as shown for Total below.
Variable | Type | Length | Format | Informat | Label |
|---|---|---|---|---|---|
Policy | Num | 8 | Policy Number | ||
Total | Num | 8 | DOLLAR8.2 | COMMA10. | Total Balance |
Name | Char | 20 | Patient Name |
Usually you have to specify the maximum width (w) of the value to be written. Depending on the particular format, you may also need to specify the number of decimal places (d) to be written. For example, to display the value 5678 as 5,678.00 in a report, you can use the COMMA8.2 format, which specifies a width of 8 including 2 decimal places.
Whereas formats write values out using some particular form, informats read data values in certain forms into standard SAS values. Informats determine how data values are read into a SAS data set. You must use informats to read numeric values that contain letters or other special characters.
For example, the numeric value $12,345.00 contains two special characters, a dollar sign ($) and a comma (,). You can use an informat to read the value while removing the dollar sign and comma, and then store the resulting value as a standard numeric value. For Total below, the COMMA10. informat is specified.
Variable | Type | Length | Format | Informat | Label |
|---|---|---|---|---|---|
Policy | Num | 8 | Policy Number | ||
Total | Num | 8 | DOLLAR8.2 | COMMA10. | Total Balance |
Name | Char | 20 | Patient Name |
A variable can have a label, which consists of descriptive text up to 256 characters long. By default, many reports identify variables by their names. You may want to display more descriptive information about the variable by assigning a label to the variable.
For example, you can label Policy as Policy Number, Total as Total Balance, and Name as Patient Name to display these labels in reports.
Variable | Type | Length | Format | Informat | Label |
|---|---|---|---|---|---|
Policy | Num | 8 | Policy Number | ||
Total | Num | 8 | DOLLAR8.2 | COMMA10. | Total Balance |
Name | Char | 20 | Patient Name |
You may even want to use labels to shorten long variable names in your reports!
When you start SAS, by default several primary windows are available to you. These include the Explorer, Log, Output, Results, and code editing window(s). The window you use to edit your SAS programs may vary, depending on your operating system and needs.
You use these SAS windows to explore and manage your files, to enter and submit SAS programs, to view messages, and to view and manage your output.
We'll tour each of these windows shortly.
Your operating environment, and any options that you use when you start SAS, determine
which of the main SAS windows are displayed by default
their general appearance
their position.
SAS windows have many features that help you get your work done. For example, you can
maximize, minimize, and restore windows
use pull-down menus, pop-up menus, and toolbars
get more help.
You're probably familiar with most of these features, but you might want to check the tips at the bottom of this page.
In the Windows and OS/2 environments, you can click the Minimize button to send a window that you aren't using to the SAS window bar. To restore the window to its former position, click the corresponding button on the SAS window bar.
In other operating environments, minimizing the window shrinks it to an icon.
In the Windows and OS/2 environments, the Explorer and Results windows are docked by default, so they can be resized but not minimized. If you prefer, you can select Window
In SAS, you can issue commands by
making selections from a menu bar
by typing commands in a command box (or Toolbox) or on a command line.
In most operating environments, SAS displays a menu bar by default. In the Windows environment, the menu bar selections correspond to the active window. To display a menu bar if it is not displayed, you can type pmenus in the command box (or ToolBox) or on the command line.
In all operating environments, SAS displays a command box (or ToolBox) or command line by default. You can display a command line in a particular window by activating that window and then using the Tools menu as indicated below:
In the Windows environment, select Tools
OptionsPreferences, then select the View tab and select the Command line checkbox.In the UNIX, VMS, and z/OS environments, select Tools
OptionsTurn Command Line On.In the z/OS environment, you can display both a command line and a menu bar simultaneously in a window by selecting Tools
OptionsCommand….
In the Windows, UNIX, and VMS operating environments, you can also display a command line in a window by activating the window, typing command in the command box (or ToolBox), and pressing Enter.
Pop-up menus are context sensitive; they list actions that pertain only to a particular screen region or selection. Generally, you display pop-up menus by clicking the right mouse button. If you like, you can specify a function key to open pop-up menus. Simply select Tools
To open a pop-up menu in the z/OS or CMS operating environments, type ? in the selection field beside the item.
Help is available for all windows in SAS. From the Help menu, you can access comprehensive online help and documentation for SAS, or you can access task-oriented help for the active window. The Help menu is discussed in more detail later in this chapter.
You can customize many features of the SAS workspace such as toolbars, pop-up menus, icons, and so on. Select the Tools menu to explore some of the customization options that are available.
You'll practice using features of SAS windows throughout this chapter. Now let's look at each of the main SAS windows individually.
In the Explorer window, you can view and manage your SAS files, which are stored in SAS data libraries. Recall that the library name is a logical name for the physical location of the files (such as a directory). You can think of the library name as a temporary nickname or shortcut.
You use the Explorer window to
create new libraries and SAS files
open any SAS file
perform most file management tasks such as moving, copying, and deleting files
create shortcuts to files that were not created with SAS.
Notice that the Explorer window displays a tree view of its contents.
You can display the Explorer window by selecting View
You can find your way around the Explorer window by double-clicking folders to open them and see their contents. You can also use pop-up menus to perform actions on a file (such as viewing its properties, or copying it). Pop-up menus contain different options for different file types.
You can use the following editors to write and edit SAS programs:
the Enhanced Editor window
the Program Editor window
the SAS Notepad window
the host editor of your choice.
This training focuses on the two SAS code editing windows: the Enhanced Editor and the Program Editor windows. The Enhanced Editor is available only in the Windows environment.
The features of both editors are described below. In the remaining chapter and in future chapters, the general term code editing window will be used to refer to your preferred SAS code editing window.
In the Windows operating environment, an Enhanced Editor window opens by default. You can use the Enhanced Editor window to enter, edit, and submit SAS programs. The initial window title is Editor - Untitledn until you open a file or save the contents of the editor to a file. Then the window title changes to reflect that filename. When the contents of the editor are modified, an asterisk is added to the title.
You can redisplay or open additional Enhanced Editor windows by selecting View
In the Enhanced Editor, you can perform standard editing tasks such as
opening SAS programs in various ways, including drag and drop
entering, editing, and submitting SAS programs
using the command line or menus
saving SAS programs
clearing contents.
In addition, the Enhanced Editor provides useful editing features, including
color coding and syntax checking of the SAS programming language
expandable and collapsible sections
recordable macros
support for keyboard shortcuts (Alt or Shift plus keystroke)
multi-level undo and redo.
For more information about the Enhanced Editor, open or activate the Enhanced Editor window, then select Help
In the Enhanced Editor and the SAS Notepad window, the code does not disappear when you submit it.
To clear any of these windows, you can activate the window and select Edit
As in the Enhanced Editor window, in the Program Editor window you enter, edit, and submit SAS programs. You can also open existing SAS programs. You can display the Program Editor window by selecting View
As in the Enhanced Editor window, in the Program Editor window you can perform standard editing tasks such as
opening SAS programs in various ways, including drag and drop
entering, editing, and submitting SAS programs
using the command line or menus
saving SAS programs
clearing contents
recalling submitted statements.
However, the Program Editor does not provide some features of the enhanced Editor, such as color-coding and syntax checking (this feature is available in SAS 9.2), expandable and collapsible sections, and recordable macros.
For more information about these features, open or activate the Program Editor window, then select Help
At any time you can clear program code from the Program Editor window by activating the window and selecting Edit
When you submit SAS programs in the Program Editor window, the code in the window is automatically cleared.
The Log window displays messages about your SAS session and about any SAS programs that you submit. You can display the Log window by selecting View
In the previous practice, you submitted a SAS program that produced log messages similar to those shown above.
You can create two basic types of SAS output:
a listing, which is traditional SAS output
an HTML document.
In the Output window, you browse listing output from SAS programs that you submit. (You can use a browser to view HTML output.)
By default, the Output window is positioned behind the code editing and Log windows. When you create output, the Output window automatically moves to the front of your display.
You can display the Output window at any time by selecting View
Not all SAS programs create output in the Output window. Some open interactive windows. Others, such as the programs that you submitted earlier in this chapter, only produce messages in the Log window.
To remove the message and view the remaining output, simply scroll to the bottom of the output.
The Results window helps you navigate and manage output from SAS programs that you submit. You can view, save, and print individual items of output.
On most operating systems, the Results window is positioned behind the Explorer window and is empty until you submit a SAS program that creates output. Then the Results window moves to the front of your display. You can display the Results window at any time by selecting View
The Results window displays separate icons for listing output and HTML output. In the example below, the first Print folder contains both types of output.
Earlier in this chapter, you saw that SAS files are stored in libraries. By default, SAS defines several libraries for you (including Sashelp, Sasuser, and Work). You can also define additional libraries.
Sashelp | a permanent library that contains sample data and other files that control how SAS works at your site. This is a read-only library. |
Sasuser | a permanent library that contains SAS files in the Profile catalog that store your personal settings. This is also a convenient place to store your own files. |
Work | a temporary library for files that do not need to be saved from session to session. |
You can also define additional libraries. When you define a library, you indicate the location of your SAS files to SAS. Once you define a library, you can manage SAS files within it.
When you delete a SAS library, the pointer to the library is deleted, and SAS no longer has access to the library. However, the contents of the library still exist in your operating environment.
To define a library, you assign a library name to it and specify a path, such as a directory path. (In some operating environments you must create the directory or other storage location before defining the library.)
You also specify an engine, which is a set of internal instructions that SAS uses for writing to and reading from files in a library.
You've seen that the Explorer window gives you access to your SAS files. You can also create a file shortcut to an external file.
An external file is a file that is created and maintained in your host operating environment. External files contain data or text, such as
SAS programming statements
records of raw data
procedure output.
SAS can use external files, but they are not managed by SAS.
A file shortcut (or fileref) is an optional name that is used to identify an external file to SAS. File shortcuts are stored in the File Shortcuts folder in the Explorer window. You can use a file shortcut to open, browse, and submit a file.
When you delete a file shortcut, the pointer to the file is deleted, and SAS no longer has access to the file. However, the file still exists in your operating environment.
Along with windows for working with your SAS files and SAS programs, SAS provides a set of ready-to-use solutions, applications, and tools. You can access many of these tools by using the Solutions and Tools menus.
For example, earlier in this chapter you opened the Sashelp.Prdsale table, which was displayed in the table editor by default. You can also open the table editor from the Tools menu. Then you can enter, browse, or edit data.
You've learned to use SAS windows to perform common SAS tasks. As you begin working in SAS, be sure to take advantage of the different types of online help that are available from the Help menu.
Using This Windowis task-oriented help for the active window.SAS Help and Documentationis a complete guide to syntax, examples, procedures, concepts, and what's new.Getting Started tutorialsare listed under Help for products where they are available.Selecting
Learning SAS programmingenables you to create data that is used in online training courses, and displays SAS OnlineTutor if you have a site license.If you have Internet access,
SAS on the Webprovides links to information including Technical Support and Frequently Asked Questions.
SAS programs consist of two types of steps: DATA steps and PROC (procedure) steps. These two steps, alone or combined, form most SAS programs. A SAS program can consist of a DATA step, a PROC step, or any combination of DATA and PROC steps. DATA steps typically create or modify SAS data sets, but they can also be used to produce custom-designed reports. PROC steps are pre-written routines that enable you to analyze and process the data in a SAS data set and to present the data in the form of a report. They sometimes create new SAS data sets that contain the results of the procedure.
SAS programs consist of SAS statements. A SAS statement usually begins with a SAS keyword and always ends with a semicolon. A DATA step begins with the keyword DATA. A PROC step begins with the keyword PROC. SAS statements are free-format, so they can begin and end anywhere on a line. One statement can continue over several lines, and several statements can be on a line. Blanks or special characters separate "words" in a SAS statement.
When you submit a SAS program, SAS reads SAS statements and checks them for errors. When it encounters a subsequent DATA, PROC, RUN, or QUIT statement, SAS executes the previous step in the program.
Each time a step is executed, SAS generates a log of the processing activities and the results of the processing. The SAS log collects messages about the processing of SAS programs and about any errors that occur.
The results of processing can vary. Some SAS programs open an interactive window or invoke procedures that create output in the form of a report. Other SAS programs perform tasks such as sorting and managing data, which have no visible results other than messages in the log.
Every SAS file is stored in a SAS library, which is a collection of SAS files such as SAS data sets and catalogs. In some operating environments, a SAS library is a physical collection of files. In others, the files are only logically related. In the Windows and UNIX environments, a SAS library is typically a group of SAS files in the same folder or directory.
Depending on the libref you use, you can store SAS files in temporary SAS libraries or in permanent SAS libraries.
Temporary SAS files that are created during the session are held in a special work space that is assigned the default libref Work. If you don't specify a libref when you create a file (or if you specify Work), the file is stored in the temporary SAS library. When you end the session, the temporary library is deleted.
To store files permanently in a SAS library, you assign it a libref other than the default Work. For example, by assigning the libref Clinic to a SAS library, you specify that files within the library are to be stored until you delete them.
To reference a SAS file, you use a two-level name, libref.filename. In the two-level name, libref is the name for the SAS library that contains the file, and filename is the name of the file itself. A period separates the libref and filename.
To reference temporary SAS files, you specify the default libref Work, a period, and the filename. Alternatively, you can simply use a one-level name (the filename only) to reference a file in a temporary SAS library. Referencing a SAS file in any library except Work indicates that the SAS file is stored permanently.
SAS data set names can be 1 to 32 characters long, must begin with a letter (A-Z, either uppercase or lowercase) or an underscore (_), and can continue with any combination of numbers, letters, or underscores.
For many of the data processing tasks that you perform with SAS, you access data in the form of a SAS data set and use SAS programs to analyze, manage, or present the data. Conceptually, a SAS data set is a file that consists of two parts: a descriptor portion and a data portion. Some SAS data sets also contain one or more indexes, which enable SAS to locate records in the data set more efficiently.
The descriptor portion of a SAS data set contains information about the data set.
The data portion of a SAS data set is a collection of data values that are arranged in a rectangular table. Observations in the data set correspond to rows or data lines in a raw data file or in an external database. An observation is the information about each object in a SAS data set. Variables in the data set correspond to columns in a raw data file or in an external database. A variable is the set of data values that describe a particular characteristic. If a data value is unknown for a particular observation, a missing value is recorded in the SAS data set.
In addition to general information about the data set, the descriptor portion contains attribute information for each variable in the data set. The attribute information includes the variable's name, type, and length. A variable's type determines how missing values for a variable are displayed by SAS. For character variables, a blank represents a missing value. For numeric variables, a period represents a missing value. You can also specify format, informat, and label attributes for variables.
You use the following windows to explore and manage your files, to enter and submit SAS programs, to view messages, and to view and manage your output.
Use this window … | To … |
|---|---|
Explorer | view your SAS files create new libraries and SAS files perform most file management tasks such as moving, copying, and deleting files create shortcuts to files that were not created with SAS |
Enhanced Editor (code editing window) | enter, edit, and submit SAS program |
| |
Program Editor (code editing window) | enter, edit, and submit SAS programs |
Log | view messages about your SAS session and about any SAS programs that you submit |
Output | browse output from SAS programs |
Results | navigate and manage output from SAS programs view, save, and print individual items of output |
Before referencing SAS files, you must assign a name (libref, or library reference) to the library in which the files are stored (or specify that SAS is to assign the name automatically).
You can store SAS files either temporarily or permanently.
Variable names follow the same rules as SAS data set names. However, your site may choose to restrict variable names to those valid in Version 6 SAS, to uppercase variable names automatically, or to remove all restrictions on variable names.
Select the best answer for each question. After completing the quiz, you can check your answers using the answer key in the appendix.
How many observations and variables does the data set below contain?
3 observations, 4 variables
3 observations, 3 variables
4 observations, 3 variables
can't tell because some values are missing
How many program steps are executed when the program below is processed?
data user.tables; infile jobs; input date name $ job $; run; proc sort data=user.tables; by name; run; proc print data=user.tables; run;
three
four
five
six
What type of variable is the variable AcctNum in the data set below?
numeric
character
can be either character or numeric
can't tell from the data shown
What type of variable is the variable Wear in the data set below, assuming that there is a missing value in the data set?
numeric
character
can be either character or numeric
can't tell from the data shown
Which of the following variable names is valid?
4BirthDate
$Cost
_Items_
Tax-Rate
Which of the following files is a permanent SAS file?
Sashelp.PrdSale
Sasuser.MySales
Profits.Quarter1
all of the above
In a DATA step, how can you reference a temporary SAS data set named Forecast?
Forecast
Work.Forecast
Sales.Forecast (after assigning the libref Sales)
only a and b above
What is the default length for the numeric variable Balance?
5
6
7
8
How many statements does the following SAS program contain?
proc print data=new.prodsale label double; var state day price1 price2; where state='NC'; label state='Name of State'; run;three
four
five
six
What is a SAS library?
collection of SAS files, such as SAS data sets and catalogs
in some operating environments, a physical collection of SAS files
in some operating environments, a logically related collection of SAS files
all of the above