How generate variable that indicates current and prior event occurrence for id in panel data

[Erik Aadland]

Dear Statalist.

I am trying to generate a variable *wanted* that takes on the value of 1 for each actor_id, and all subsequent observations for each actor_id, that experiences event == 1. Event == 1 may occur several times in the panel for a given actor_id, so I am trying to generate *wanted* based on the first occurrence of event==1 for each actor_id.

My data structure looks like this:

time	group_id	actor_id	event	wanted
1	1	1
1	1	2
1	2	3
1	2	4	1	1
2	3	1	1	1
2	3	5
2	3	3
2	4	4		1
2	4	8
3	5	1		1
3	5	2
3	6	3
3	6	4	1	1

Any and all input on this problem would be much appreciated.

Thank you so much.

Regards,
Erik

[Nick Cox]

http://www.stata.com/support/faqs/da...t-occurrences/

[Erik Aadland]

Thank you, Nick.

I applied the following code following the suggested FAQ:

by actor_id (time), sort : gen byte wanted = sum(event) == 1


The results I the code generates are as follows:

time	group_id	actor_id	event	wanted
1	1	1	0	0
2	3	1	1	1
3	5	1	0	1
1	1	2	0	0
3	5	2	0	0
1	2	3	0	0
2	3	3	0	0
3	6	3	0	0
1	2	4	1	1
2	4	4	0	1
3	6	4	1	0
2	3	5	0	0
2	4	8	0	0

The code does not generate wanted==1 for actor_id ==4 at time == 3.

Is there a way to tweak the code to generate wanted == 1 for actor_id ==4 at time==3 as well?

Sincerely,
Erik

[William Lisowski]

The sum() function generates running totals, so for actor_id==4 at time==3 sum(event) = 2 . What you want is

by actor_id (time), sort : gen byte wanted2 = sum(event) >= 1

[Erik Aadland]

Thank you, William.
That worked splendidly.

Sincerely,
Erik.