Introduction to Do Loop in SAS

In SAS, a Do Loop is a repetitive control structure used to execute a block of code repeatedly while a condition holds true. It is used when we want to perform a certain operation a number of times or until a condition is met.

The syntax for a Do Loop in SAS is as follows:

do index_variable = start_value to end_value <by increment>;
   statements;
end;

• index_variable is a temporary variable that is created by the Do Loop and takes on values from start_value to end_value.
• start_value is the initial value for index_variable.
• end_value is the final value for index_variable.
• increment is an optional argument that specifies the amount by which index_variable is incremented each time through the loop. The default value is 1.

The statements in the Do Loop can be any valid SAS statements, including Data Step statements, Macro statements and SQL statements.

Below is an example of a Do Loop in SAS that prints the squares of the numbers from 1 to 10:

data square;
   do i = 1 to 10;
      square = i ** 2;
      output;
   end;
run;

In this example, a new dataset named "square" is created, and a Do Loop is used to iterate through the values of i from 1 to 10. The statement square = i ** 2 calculates the square of i and assigns it to the variable square. The statement output writes the current observation to the output dataset.

The resulting dataset "square" would look like:

| i | square | |---|--------| | 1 | 1 | | 2 | 4 | | 3 | 9 | | 4 | 16 | | 5 | 25 | | 6 | 36 | | 7 | 49 | | 8 | 64 | | 9 | 81 | | 10| 100 |

Overall, Do Loops provide an easy and efficient way to execute repetitive code in SAS. By specifying the start value, end value, and optionally the increment, we can tailor the loop to specific needs.