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From |
Nick Cox <njcoxstata@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: elapsed time between incidents |

Date |
Tue, 19 Feb 2013 23:32:15 +0000 |

Here's another way to do it: gen notincident = missing(incident) bysort id (notincident day) : gen elapsed2 = day - day[_n-1] if !notincident Nick On Tue, Feb 19, 2013 at 11:19 PM, Nick Cox <njcoxstata@gmail.com> wrote: > I don't think anyone can be expected to choose the same words as me, > so searching for this inevitably seems difficult. > > Nick > > On Tue, Feb 19, 2013 at 9:34 PM, Steven Archambault > <archstevej@gmail.com> wrote: >> Okay, thanks for this. I apologize for not finding the tip prior to >> posting. My chosen search words were off! >> >> On Tue, Feb 19, 2013 at 2:08 PM, Nick Cox <njcoxstata@gmail.com> wrote: >>> This kind of problem was discussed in my posts >>> >>> http://www.stata.com/statalist/archive/2011-01/msg00999.html >>> >>> http://www.stata.com/statalist/archive/2012-08/msg00633.html >>> >>> and in a Tip >>> >>> Cox, N.J. 2011. Stata tip 101: Previous but different. Stata Journal >>> 11(3): 472-473. >>> >>> No doubt there are other references. >>> >>> Here's some code: >>> >>> . clear >>> >>> . input id day incident >>> >>> id day incident >>> 1. 1 1 6 >>> 2. 1 2 . >>> 3. 1 3 . >>> 4. 1 4 . >>> 5. 1 5 8 >>> 6. 1 6 . >>> 7. 1 7 5 >>> 8. end >>> >>> . bysort id (day): gen prev = day[_n-1] if incident[_n-1] < . >>> (5 missing values generated) >>> >>> . by id: replace prev = prev[_n-1] if missing(prev) >>> (4 real changes made) >>> >>> . gen elapsed = day - prev if incident < . >>> (5 missing values generated) >>> >>> . l, sep(0) >>> >>> +--------------------------------------+ >>> | id day incident prev elapsed | >>> |--------------------------------------| >>> 1. | 1 1 6 . . | >>> 2. | 1 2 . 1 . | >>> 3. | 1 3 . 1 . | >>> 4. | 1 4 . 1 . | >>> 5. | 1 5 8 1 4 | >>> 6. | 1 6 . 5 . | >>> 7. | 1 7 5 5 2 | >>> +--------------------------------------+ >>> >>> The nub of the matter is that the previous event can be picked up in >>> the following observation for the same identifier. After that we just >>> copy down as required in a cascade. >>> >>> FAQ . . . . . . . . . . . . . . . . . . . . . . . Replacing missing values >>> . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . N. J. Cox >>> 2/03 How can I replace missing values with previous or >>> following nonmissing values? >>> http://www.stata.com/support/faqs/data/missing.html >>> >>> -by:- makes doing this by panels no more difficult than doing it if >>> there were no panels. >>> >>> Steve said non-zero, but his example implies non-missing; whatever the >>> exact condition is can no doubt be substituted easily. >>> >>> Nick >>> >>> On Tue, Feb 19, 2013 at 8:45 PM, Steven Archambault >>> <archstevej@gmail.com> wrote: >>> >>>> 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. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**References**:**st: elapsed time between incidents***From:*Steven Archambault <archstevej@gmail.com>

**Re: st: elapsed time between incidents***From:*Nick Cox <njcoxstata@gmail.com>

**Re: st: elapsed time between incidents***From:*Steven Archambault <archstevej@gmail.com>

**Re: st: elapsed time between incidents***From:*Nick Cox <njcoxstata@gmail.com>

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