Finding Shortcuts in Programming

Review of SAS Tools

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

creates a named, ordered list of variables that exists for processing of the current DATA step. The array-name must be a valid SAS name. Each variable is the name of a variable to be included in the array. Number-of-variables is the number of variables listed.

When you place a variable in an array, the variable can also be accessed by array-name {position}, where position is the position of the variable in the list (from 1 to number-of-variables). This way of accessing the variable is called an array reference, and the position is known as the subscript of the array reference. After you list a variable in an ARRAY statement, programming statements in the same DATA step can use either the original name of the variable or the array reference.

This documentation uses curly braces around the subscript. Parentheses ( ) are also acceptable, and square brackets [ ] are acceptable on operating environments that support those characters. Refer to the documentation provided by the vendor for your operating environment to determine the supported characters.

DO; ...SAS statements... END;

treats the enclosed SAS statements as a unit. A group of statements beginning with DO and ending with END is called a DO group. DO groups usually appear in THEN clauses or ELSE statements.

DO index-variable=1 TO number-of-variables-in-array; ... SAS statements... END;

is known as an iterative DO loop. In each execution of the DATA step, an iterative DO loop is processed repeatedly (is iterated) based on the value of index-variable. To create an index variable, simply use a SAS variable name in an iterative DO statement.

When you use iterative DO loops for array processing, the value of index-variable usually starts at 1 and increases by 1 before each iteration of the loop. When the value becomes greater than the number-of-variables-in-array (usually the number of variables in the array being processed), SAS stops processing the loop and proceeds to the next statement in the DATA step.

In array processing, the SAS statements in an iterative DO loop usually contain array references whose subscript is the name of the index variable (as in array-name {index-variable}). In each iteration of the loop, SAS replaces the subscript in the reference with the index variable's current value. Therefore, successive iterations of the loop cause SAS to process the statements on the first variable in the array, then on the second variable, and so on.

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