SAS Certified Specialist Prep Guide

Conditionally Executing DO Loops

Overview

The iterative DO statement specifies a fixed number of iterations for the DO loop. However, there are times when you want to execute a DO loop until a condition is reached or while a condition exists, but you do not know how many iterations are needed.

Suppose you want to calculate the number of years required for an investment to reach $50,000. In the DATA step below, using an iterative DO statement is inappropriate because you are trying to determine the number of iterations required for Capital to reach $50,000.

data work.invest; 
  do year=1 to ? ; 
    Capital+2000; 
    capital+capital*.10; 
  end; 
run;

The DO WHILE and DO UNTIL statements enable you to execute DO loops based on whether a condition is true ...