SAS 9.4 Language Reference, 6th Edition

Table 4.2 Index Type Attribute Values

Value Definition

NONE The variable is not indexed.

SIMPLE The variable is part of a simple index.

COMPOSITE The variable is part of one or more composite indexes.

BOTH The variable is part of both simple and composite indexes.

extended attribute

is a user-defined attribute that is created using the XATTR ADD VAR statement in

the DATASETS procedure. For more information, see “Extended Attributes” in Base

SAS Procedures Guide.

Ways to Create Variables

Overview

These are some of the most common ways that you can create variables in a DATA step:

• Use an assignment statement.

• Read data with the INPUT statement in a DATA step.

• Specify a new variable in a FORMAT or INFORMAT statement.

• Specify a new variable in a LENGTH statement.

• Specify a new variable in an ATTRIB statement.

Note: This list is not exhaustive. For example, the SET, MERGE, MODIFY, and

UPDATE statements can also create variables.

Using an Assignment Statement

In a DATA step, you can create a new variable and assign it a value by using it for the

first time on the left side of an assignment statement. If a variable is created using an

assignment statement, both its type and length must be implicitely defined by SAS.

SAS determines the length and type of the variable from its first occurrence in the DATA

step. The variable gets the same type and length as the expression on the right side of the

assignment statement.

When the type and length of a variable are not explicitly set, SAS gives the variable a

default type and length, as shown in the examples in the following table.

Ways to Create Variables 41

Table 4.3 Resulting Variable Types and Lengths Produced When They Are Not Explicitly Set

Expression Example

Resulting

Type of X

Resulting

Length of X Explanation

Numeric

variable

length a 4;

x=a;

Numeric

variable

8 Default numeric

length (8 bytes

unless otherwise

specified)

Character

variable

length a $ 4;

x=a;

Character

variable

4 Length of source

variable

Character literal

x='ABC';

x='ABCDE';

Character

variable

3 Length of first

literal

encountered

Concatenation

of variables

length a $ 4

b $ 6

c $ 2;

x=a||b||c;

Character

variable

12 Sum of the

lengths of all

variables

Concatenation

of variables and

literal

length a $ 4;

x=a||'CAT';

x=a||'CATNIP'

;

Character

variable

7 Sum of the

lengths of

variables and

literals

encountered in

first assignment

statement

If a variable appears for the first time on the right side of an assignment statement, SAS

assumes that it is a numeric variable and that its value is missing. If no later statement

gives it a value, SAS prints a note in the log that the variable is not initialized. Instead of

issuing a note in the SAS log, you can use the VARINITCHK= system option to specify

that no note is to be written to the SAS log, or to specify that a warning or an error

message is to be written to the SAS log. If an error is set, the DATA step stops

processing. For more information, see “VARINITCHK= System Option” in SAS System

Options: Reference.

Note: A RETAIN statement initializes a variable and can assign it an initial value, even

if the RETAIN statement appears after the assignment statement.

when you create a variable using the INPUT statement, it is considered “explicitely”

declared even if you do not explicitly assign the length.

Reading Data with the INPUT Statement in a DATA Step

When you read raw data in SAS by using an INPUT statement, you define variables

based on positions in the raw data. You can use one of the following methods with the

INPUT statement to provide information to SAS about how the raw data is organized:

• column input

• list input (simple or modified)

• formatted input

42 Chapter 4 • SAS Variables