53.The following SAS program is submitted:
data WORK.TOTAL_SALARY;
retain Total;
set WORK.SALARY;
by Department;
if First.Department
then Total=0;
Total=sum(Total, Wagerate);
if Last.Total;
run;
What is the initial value of the variable Total?
A. 0
B. Missing
C. The value of the first observations Wagerate
D. Cannot be determined from the information given
Answer: B
求大神解析一下,retain 的意义和用法!以及本程序答案的解析!
最后想问问,base 70题有没有比较详细的解析啊!我这个版本只有简单的答案!表示非常费解!