求问各位大佬们，sas使用数组时,显示数组中的变量全部未初始化，这是为什么呀？代码应该怎么改呢？

以下是代码：
data Tmp1.sleep_final8;
set Tmp1.sleep_final7;
array shiftwork[20] n_22620_0_0        n_22620_0_1 n_22620_0_2 n_22620_0_3 n_22620_0_4 n_22620_0_5 n_22620_0_6 n_22620_0_7 n_22620_0_8 n_22620_0_9 n_22620_0_10 n_22620_0_11 n_22620_0_12 n_22620_0_13 n_22620_0_14 n_22620_0_15 n_22620_0_16 n_22620_0_18 n_22620_0_19 n_22620_0_32;
do i=1 to 20;
shifttotal=sum(of shiftwork1-shiftwork20);
if shifttotal=0 then worktotal=0;
if shiftwork=1 and dayshift=9 then worktotal=.;
end;
run;