Hi all:

I want to keep variable use condition with next year and last year data.

Sample

ID YEAR CONDITION
A 1990 .
B 1990 .
B 1991 .
B 1992 1
B 1993 .
C 1990 .
.


when I use" keep if", the result is B 1992 1, but I want result include both last year and next year data like:
" B 1991.
B 1992 1
B 1993. "

Many thanks