在用<DEA各种模型原理及stata代码实现>中SBM模型代码时报错

在用中SBM模型代码时报错

sbmeff x1 x2  = y1 y2 :z1 z2 ,dmu(id) time(t) sav(sbm_t,replace)
sbmeff x1 x2  = y1 y2 :z1 z2 ,dmu(id) sav(sbm_g,replace)
merge m:m id  using sbm_g
rename TE TE_G
drop _merge
merge 1:1 id t using sbm_t
drop _merge
xtset dmu t
tostring t, generate(time1)
gen lyear = l.t
tostring lyear, generate(time2)
gen time = time1 + "~" +time2
gen TFPCH = TE_G / l.TE_G
gen TECH = TE/l.TE
gen BPC = TFPCH / TECH
keep if TFPCH != .
list city time TFPCH TECH BPC

运行结果及报错内容 ：

. do "C:\Users\dell\AppData\Local\Temp\STD4978_000000.tmp"

. sbmeff x1 x2 = y1 y2 :z1 z2 ,dmu(id) time(t) sav(sbm_t,replace)
: 3499 sbmu() not found
r(3499);

end of do-file

r(3499);