How to skip merging empty master datasets in a loop?

[Jae Li]

Dear Stata experts,

I'd like to ask a question about merging datasets in a loop when no observations merged and please see my code here:

forval i = 1/20{
preserve
bsample

reg y x1 x2 i.sic3 i.year, vce(robust)

gen b_x1 = _b[x1]
gen se_x1 = _se[x1] 
gen t_x1 = abs(b_x1 / se_x1)

* keep significant coefficients
keep if t_x1 >= 1.65

* if no observations left, exit
 if c(rc) != 0 {
  exit (c(rc))
 }

 else {
   gen index = `i'
    keep gvkey fyear 
    
    merge m:1 gvkey fyear using "base.dta"
    keep if _merge == 3
    drop _merge

However, it shows an error message after merging. Is there any advice on how to resolve this issue?

Result        Number    of obs
            
Not matched            49,576
from master            0    (_merge==1)
from using            49,576    (_merge==2)

Matched            0    (_merge==3)
            
(49,576 observations    deleted)
no observations
r(2000);

Many thanks!
Jae

[Clyde Schechter]

Although this is not an exact duplicate post, the main question posed is the same. If interested in following, see https://www.statalist.org/forums/for...in-a-500-loops.