sas base 70题的第53题原题如下:
The following SAS program is submitted:
data WORK.TOTAL_SALARY;
retain Total;
set WORK.SALARY;
by Department;
ifFirst.Department
then Total=0;
Total=sum(Total,Wagerate);
if Last.Total;
run;
What is the initial value of the variableTotal?
A. 0
B. Missing
C. The value of the first observationsWagerate
D. Cannot be determined from theinformation given
答案:B
答案应该怎么解读?
这里面是因为by 的变量是department,所以last.total的值是miss,是这样吗?