A SAS programmer writes: DATA output; SET input; IF _N_ = 1 THEN DO; ... END; RUN; What is the purpose of the IF _N_ = 1 condition?
Select an answer to reveal the explanation.
Short Explanation
Here's the deal — b is correct because _N_ is a SAS automatic variable that counts the iteration of the DATA step loop — it equals 1 only on the first iteration when the first observation is being read. This is commonly used to initialize variables, open files, or execute setup logic exactly once.
Full Explanation
B is correct because _N_ is a SAS automatic variable that counts the iteration of the DATA step loop — it equals 1 only on the first iteration when the first observation is being read. This is commonly used to initialize variables, open files, or execute setup logic exactly once. A is wrong because _N_ counts iterations, not variables. C is wrong because _N_ is automatically incremented by SAS, not assigned by the programmer. D is wrong because the condition controls when the DO block executes, not which observations are output.