用sas做完时序模型后怎么对原数据进行预测？
forecast lead=6 interval=month id=time out=b;
run;
proc print data=b;
run;

data c;
set b;
people=exp(lp)
forecast=exp(forecast+std*std/2)
l95=exp(l95);
u95=exp(u95);
run;
为什么总是说我的语法错误？