公式的类型是这样的（图片放不出来，我放在评论里吧呜呜）
然后按着公式写了这个代码，总是报错

proc sql;
     create table demo_2 as
     select distinct permno,datadate, csho, ajex,
     lag(csho,1,0) over(order by permno) lag_csho1
     lag(csho,2,0) over(order by permno) lag_csho2
     lag(ajex,1,0) over(order by permno) lag_ajex1
     lag(ajex,2,0) over(order by permno) lag_ajex2
     log((lag_csho1 * lag_csho2)/(lag_ajex1 * lag_ajex2)) as nsi,ret
     from  Rdata.funda_1;
quit;

C=log((At-1*Bt-1)/(At-2*Bt-2))
没办法放照片呜呜，t-1和t-2分别都是下标