Fill null values

[Esteban Jara]

Hello. I have a data structure like the one in the figure. For the null values of the variable uv I need to fill with the same values that appear as non-null ("20A"), for the same data group comuna-street-numdom. How can I do it? Thanks

[Ali Atia]

 bysort comuna street numdom (uv): replace uv = uv[_N] if uv == ""

[Esteban Jara]

Thank you!