How to replace a missing value with a value in certain row

[Shin Kang]

I need to fill up the missing values for the variable (v1). The variables are {country, v1, v2}

I have sporadic missing values in v1, but v1 and v2 have high correlation, so I can fill up v1 based on the order statistics of v2.
For example, I want to replace v1[1] to v2 if v2_rank == 1

I tried
replace v1 = v2[v2_rank] if v1 == .
replace v1 = v2[_v2_rank] if v1 == .


But it does not work...

country	v1	v2	v1_rank	v2_rank
SG	.	11	.	1
NL	10	10	1	2
HK	9	9	2	3
GB	8	8	3	4

[Jared Greathouse]

Use dataex please. I need to see your actual data, otherwise I can't help you. "Does not work" is super vague.

[Shin Kang]

replace v1 = v2[v2_rank] if v1 == .

and

replace v1 = v2[_v2_rank] if v1 == .

But none of them works...

country	v1	v2	v1_rank	v2_rank
SG	.	11	.	1
NL	10	10	1	2
HK	9	9	2	3
GB	8	8	3	4

[Øyvind Snilsberg]

replace v1 = v2 if v1 == .