Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: st: elapsed time between incidents
From
Nick Cox <[email protected]>
To
[email protected]
Subject
Re: st: elapsed time between incidents
Date
Tue, 19 Feb 2013 23:19:38 +0000
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
<[email protected]> 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 <[email protected]> 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
>> <[email protected]> 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/