Re: st: elapsed time between incidents

[David Kantor <kantor.d@att.net>]

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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