Hi all,

Here is an example:

individual value
1 .
1 21
2 51
2 .
2 .
3 .
3 15
3 .

How can we fill in missing values of age by individuals?

individual value
1 20
1 21
2 51
2 52
2 53
3 14
3 15
3 16

Thanks in advance,
David