SAS Base (54)

Consider the following data step:

set SASHELP.CLASS(obs=5);
retain City ‘Beverly Hills’;

The computed variables City and State have their values assigned using two different methods, a RETAIN statement and an Assignment statement. Which statement regarding this program is true?

A. The RETAIN statement is fine, but the value of City will be truncated to 8 bytes as the LENGTH statement has been omitted.
B. Both the RETAIN and assignment statement are being used to initialize new variables and are equally efficient. Method used is a matter of programmer preference.
C. The assignment statement is fine, but the value of City will be truncated to 8 bytes as the LENGTH statement has been omitted.
D. City’s value will be assigned one time, State’s value 5 times.

Check Answer
Answer: D

注解:Both RETAIN statement and Assignment (=) statement can be used to assign values, but there are a few differences.

1. As RETAIN statement assigns the value at compile time, the code will be executed once and only once. Assignment statement, however, respecifies the value in every iteration.
2. SAS automatically sets variables that are assigned values by an assignment statement to missing before each iteration of the DATA step. On the contrary, RETAIN statement retains the value from one iteration to the next.

AS this program reads the first 5 observations (5 iterations) in CLASS data set,  the value of State is specified 5 times, and the variable is reset to missing when SAS begins to read the next observation. City is initialized as ‘Beverly Hills’ before DATA step and won’t be reset to missing.

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