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Re: st: RE: Creating repeated index


From   TA Stat <tastat@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: Creating repeated index
Date   Wed, 20 Oct 2010 23:26:51 +0700

Thanks a lot, it works this time.

Pete

On Wed, Oct 20, 2010 at 11:04 PM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> Try
>
> bysort studentid visitdate : gen first = _n == 1
> by studentid : replace first = sum(first)
>
> Nick
> n.j.cox@durham.ac.uk
>
> Pete
>
> It doesn't work. The index should start with "1" for every student.
>
> On Wed, Oct 20, 2010 at 10:36 PM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
>> egen index = group(studentid visitdate)
>>
>> Nick
>> n.j.cox@durham.ac.uk
>>
>> Pete
>>
>> I am trying to create an index/running number based upon same value of
>> one variable, i.e., visit date.  Different visit date will have
>> different index/running number.  I can do it by finding duplicates and
>> drop them, then create an index and save as a new file, then merge a
>> new file with the original one.  However, I want to know whether there
>> is a short cut to do this.  My data will looks like this.
>>
>> StudentID     Visit Date     Item       Index
>> 1                  1/1/2010        A            1
>> 1                  1/1/2010        B            1
>> 1                  2/4/2010        A            2
>> 1                  2/4/2010        B            2
>> 1                  2/4/2010        C            2
>> 2                  4/1/2010        A            1
>> 2                  4/1/2010        B            1
>> 2                  4/1/2010        C            1
>> 2                  3/3/2010        A            2
>> 2                  3/3/2010        E            2
>>
>>
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