SAS Certification Prep Guide, 4th Edition

Nesting DO Loops

Iterative DO statements can be executed within a DO loop. Putting a DO loop within a DO loop is called nesting.

do i=1 to 20; 
   ...more SAS statements... 
   do j=1 to 10; 
      ...more SAS statements... 
   end; 
   ...more SAS statements... 
end;

The DATA step below computes the value of a one-year investment that earns 7.5% annual interest, compounded monthly.

data work.earn; 
   Capital=2000; 
   do month=1 to 12; 
      Interest=capital*(.075/12); 
      capital+interest; 
   end; 
run;

Assume that the same amount of capital is to be added to the investment each year for 20 years. The new program must perform the calculation for each month during each of the 20 years. To do this, you can include the monthly calculations within another DO loop that executes 20 times. ...