悬赏求教一个变量编程的问题

求教下面的那个变量如何在stata中实现：
|iki,t-ik-i,t-1| is the absolute value of the difference between ik (the investment ratio) of firm i in year t and the average (第二个ik 上面应该有个横杠，不知道怎么弄出来) investment ratio of other firms in the same industry excluding firm i in year (t-1)

PS：数据为panel data，包括firmid，year，ik等数据

bys year: egen x1=total(ik)   //ki在每年的总和
bys year: gen n=_N     //公司个数
bys year: gen mean=(x1-ik)/(n-1)   //你要的均数

gen diff=abs(ik[_n]-mean[_n-1])