keep variable with condition and time series

[Han Jin]

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

[Han Jin]

Anyone could help me? So many thanks!

[Nick Cox]

Please use dataex for your data examples (FAQ Advice #12).

* Example generated by -dataex-. To install: ssc install dataex
clear
input str1 id int year byte condition
"A" 1990 .
"B" 1990 .
"B" 1991 .
"B" 1992 1
"B" 1993 .
"C" 1990 .
end

bysort id (year) : keep if condition < . | condition[_n-1] < . | condition[_n+1] < .

list

     +----------------------+
     | id   year   condit~n |
     |----------------------|
  1. |  B   1991          . |
  2. |  B   1992          1 |
  3. |  B   1993          . |
     +----------------------+

[Han Jin]

Please use dataex for your data examples (FAQ Advice #12).

* Example generated by -dataex-. To install: ssc install dataex
clear
input str1 id int year byte condition
"A" 1990 .
"B" 1990 .
"B" 1991 .
"B" 1992 1
"B" 1993 .
"C" 1990 .
end

bysort id (year) : keep if condition < . | condition[_n-1] < . | condition[_n+1] < .

list

+----------------------+
| id year condit~n |
|----------------------|
1. | B 1991 . |
2. | B 1992 1 |
3. | B 1993 . |
+----------------------+

Thank you so much! And I will use dataex next time.