Step-by-Step Programming with Base SAS 9.4, Second Edition, 2nd Edition

Performing the Same Action for a Series of

Variables

Using a Series of IF-THEN Statements

In the data set MYLIB.ATTRACTIONS, the variables Museums, Galleries, and Other

contain missing values when the tour does not feature that type of attraction. To change

the missing values to 0, you can write a series of IF-THEN statements with assignment

statements, as the following program illustrates:

/* same action for different variables */

data changes;

set mylib.attractions;

if Museums = . then Museums = 0;

if Galleries = . then Galleries = 0;

if Other = . then Other = 0;

run;

The pattern of action is the same in the three IF-THEN statements. Only the variable

name is different. To make the program easier to read, you can write SAS statements that

perform the same action several times, changing only the variable that is affected. This

technique is called array processing, and consists of the following three steps:

1. grouping variables into arrays

2. repeating the action

3. selecting the current variable to be acted upon

Grouping Variables into Arrays

In DATA step programming, you can put variables into a temporary group called an

array. To define an array, use an ARRAY statement. A simple ARRAY statement has the

following form:

ARRAY array-name{number-of-variables} variable-1 < . . . variable-n>;

Array-name is a SAS name that you choose to identify the group of variables. Number-

of-variables, enclosed in braces, tells SAS how many variables you are grouping, and

variable-1< . . . variable-n> lists their names.

Note: If you have worked with arrays in other programming languages, note that arrays

in SAS are different from those in many other languages. In SAS, an array is simply

a convenient way of temporarily identifying a group of variables by assigning an

alias to them. It is not a permanent data structure. It exists only for the duration of the

DATA step. The array-name identifies the array and distinguishes it from any other

arrays in the same DATA step. It is not a variable.

The following ARRAY statement lists the three variables Museums, Galleries, and

Other:

array changelist{3} Museums Galleries Other;

This statement tells SAS to do the following:

• make a group named CHANGLIST for the duration of this DATA step

Performing the Same Action for a Series of Variables 219