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Re: st: Finding the corresponding variable


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Finding the corresponding variable
Date   Sun, 7 Apr 2013 10:07:28 +0100

Should be

gen closest = cond(abs(datea - `when') < abs(dateb - `when'), datea, dateb)

Nick
njcoxstata@gmail.com


On 7 April 2013 09:21, Nick Cox <njcoxstata@gmail.com> wrote:
> Your problem has several similarities with that posed by David
> Ashcraft yesterday. Read the whole thread starting at
>
> http://www.stata.com/statalist/archive/2013-04/msg00225.html
>
> The closest (closer) date of two others is
>
> local when = mdy(1,1,2013)
>
> gen closest = cond(abs(datea - `when') > abs(dateb - `when'), datea, dateb)
>
> after which you can -list- it.
>
> Alternatively, given what you have,
>
> gen closest = cond(var1 < var2, datea, dateb)
>
> You need some rule for when two dates are equally close.
>
> Notes:
>
> 1. I recommend against meaningless names such as "var1", "var2",
> "var3". You put strain on yourself and anyone reading your code to
> remember what they are
>
> 2. -egen, rowmin()- is all right for what you did but using the
> -min()- function is simpler with just two arguments.
>
> Nick
> njcoxstata@gmail.com
>
> On 7 April 2013 05:24, Ching Wong <ching.y.wong@student.adelaide.edu.au> wrote:
>
>> I have TWO variables of dates, called "datea" and "dateb". I would
>> like to calculate the number of days between a particular date (says,
>> 1/01/2013) and the closest day either "datea" or "dateb".
>>
>> Firstly, I generated one variable called "var1" which is the number of
>> days between the particular date and "datea" and also generated
>> another variable called "var2" which is the number of days between the
>> particular date and "dateb".
>>
>> Then I set up another variable "var3" in order to choose the minimun
>> number of days between "var1" and "var2". By using the Command as
>> following:
>> ---> egen var3 = rowmin (var1 var2).
>>
>> My question is that after getting "var3", how I can list the
>> corresponding "datea" or "dateb"?
>> i.e. var3---> var1 or var2----> datea or dateb
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