Hello Everyone,

Again a very basic question.

dataex:

v1 v2 v3
1 12 1
1 13 2
1 15 3
2 13 4
2 14 5
2 16 6
2 17 21
2 19 22
3 12 23
3 13 24
3 17 25
1 12
1 15
2 13
2 17
2 19
3 12
3 13
3 17

In above data example, how can I replace missing values of v3 based on values which are not missing. For example, missing value of v3 where v1=1 and v2=12 should be replaced with 1 based on first observation (where v1=1, v2=12 and v3=1 is given). I want to replace all missing values in one go.

Best
Amit