At 03:45 PM 2/19/2013, Steve wrote:
Hi all,
I have unbalanced panel data where an incident (measured by a non-zero
value) occurs randomly in the panel. I want to calculate the time
(days_elapsed) between incidents. Here is an example:
id day incident days_elapsed
1 1 6 .
1 2 . .
1 3 . .
1 4 . .
1 5 8 4
1 6 . .
1 7 5 2
Thanks for any help here. I have not been able to find this.
-Steve
First, you mentioned an incident being determined by a non-zero
value, presumably in the variable name incident.
But your example seems to be based on non-missing, rather than
non-zero. I'll presume you mean non-missing.
You could try...
gen pday = day if ~mi(incident)
by id (day): replace pday = pday[_n-1] if mi(pday) & _N>1
/* you could also use -carryforward- from ssc. */
by id (day): gen days_elapsed = day- pday[_n-1] if ~mi(incident) & _n>1
HTH
--David
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