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

To |
"statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |

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

Date |
Fri, 12 Apr 2013 01:33:52 +0100 |

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 > ************************************* > > * > * 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/ * * 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: generating a variable that requires comparing two dates***From:*"Ariel Linden, DrPH" <ariel.linden@gmail.com>

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