Re: st: generating a variable that requires comparing two dates

[Nick Cox <njcoxstata@gmail.com>]

One technique that can be useful with paired dates is to -expand 2-.

See http://www.stata-journal.com/article.html?article=dm0068


Nick
njcoxstata@gmail.com


On 11 April 2013 20:16, Ariel Linden, DrPH <ariel.linden@gmail.com> wrote:
> Hi fellow listers,
>
> This may be an easy task, but I am not getting it right...
>
> I would like to generate a new variable ( by ID) that will equal 1 if there
> was an alert (triggered on the surveydate, when that surveydate was the same
> as the admitdate. The obvious problem is that the dates are not always
> aligned so a straight "bys ID: gen test if surveydate==admitdate & alert==1"
> will not always work.
>
> In the data below, the code would need to "see" that the admitdate of
> 4/6/2011 has a corresponding surveydate a few lines down where the alert==1.
> Similarly, the next admitdate is 4/20/2011, so it would need to lookup the
> corresponding surveydate and verify that alert==1.
>
> I would then like to run this code again (generating a new variable) where
> we'd look to see if there was an alert on the surveydate the day before the
> admitdate (ie., surveydate = admitdate - 1)
>
> Thanks in advance!
>
> Ariel
>
> **** example data****
>
> ID      surveydate      alert   admitdate
> 1       4/2/2011        1       4/6/2011
> 1       4/3/2011        1       4/20/2011
> 1       4/4/2011        0       4/20/2011
> 1       4/5/2011        0       4/20/2011
> 1       4/6/2011        1       4/20/2011
> 1       4/7/2011        0       4/20/2011
> 1       4/8/2011        0       4/20/2011
> 1       4/9/2011        0       4/20/2011
> 1       4/10/2011       0       4/20/2011
> 1       4/11/2011       0       4/20/2011
> 1       4/12/2011       0       4/20/2011
> 1       4/13/2011       0       4/20/2011
> 1       4/14/2011       0       4/20/2011
> 1       4/15/2011       0       4/20/2011
> 1       4/16/2011       0       4/20/2011
> 1       4/17/2011       0       4/20/2011
> 1       4/18/2011       0       4/20/2011
> 1       4/19/2011       0       4/20/2011
> 1       4/20/2011       1       4/20/2011
> 1       4/21/2011       0       4/20/2011
> *************************************
>
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