MWD检测的时候，总是分不清楚，什么时候用predict e,xb什么用predict e,res

这是这个题，下面是老师写的
rename var1 year
rename var2 y
rename var3 x
gen lny=ln(y)
gen lnx=ln(x)
reg y x year
predict y1,xb
reg lny lnx year
predict lny1,xb
gen lny2=ln(y1)
gen z=lny2-lny1
reg y x year z
gen y3=exp(lny1)
gen z2=y3-y1
reg lny lnx year z2
predict e1,xb