What is the purpose of the RETAIN statement in a DATA step?

The RETAIN statement serves a specific purpose within a DATA step in SAS programming. It is used to retain the value of a variable across iterations of the DATA step. This means that instead of resetting the variable to missing (or its default value) at the start of each iteration, the variable retains its value from the previous iteration. This is particularly useful when performing calculations that require a variable to hold its value as the data is processed row by row, such as cumulative sums or for carrying forward a value over multiple records.

For instance, if you want to calculate a running total, the RETAIN statement allows you to keep the cumulative total from one observation to the next, ensuring that each row references the updated value from its predecessor. By doing so, the data processing can build upon previous iterations, thereby facilitating more complex data manipulations.

The other choices do not accurately reflect the true function of the RETAIN statement. While permanent storage and dropping variables relate to different aspects of data management and manipulation within SAS, they do not capture the essence of how the RETAIN statement modifies variable behavior during the iterative process of a DATA step. Creating new variables based on calculations, while common in DATA steps, does not inherently require the use of the RETAIN statement,