输入下列代码之后提示invalid syntax,请问这是为什么呀?
local y "cfo"
global y `y'
local x "invA sale Dsale"
global x `x'
cap drop AB`y'
gen AB`y' = .
forvalues i = 1/$N{
qui reg `y' `x' if (sic_year==`i')
qui predict e if e(sample), res
qui replace AB`y' = e if e(sample)
drop e
}