# Re: st: variable that counts double observations..

 From "Ashim Kapoor" To statalist@hsphsun2.harvard.edu Subject Re: st: variable that counts double observations.. Date Wed, 12 Nov 2008 20:58:42 +0530

```Nick,

I know it is not exactly what is written but it does the job of
grouping 2 consecutive variables and hence can be used in the by
command. To refine it you may say

egen j=group(var)

then we will have 1 1 2 2  3 3 etc.

By the way I never got your 1st post. Email got eaten up I guess.

Thank you,
Ashim.

On Wed, Nov 12, 2008 at 8:48 PM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> The first line won't work, as already explained in my earlier posting.
>
> But suppose you had a variable with values 1 up.
>
> The second line would replace 1,2,3,4,5,6, ... with 1,1,3,3,5,5,...
> which is not what I think is being asked for.
>
> Nick
> n.j.cox@durham.ac.uk
>
> Ashim Kapoor
>
>
> egen var=_n , by(group)
> by group : replace var=var-1 if mod(var,2)==0
>
> I think this should work.
>
> What the second line says is that for every even number var should
> have the value of the previous var which is itself -1 .
>
> Can someone approve this ? I am not 100% certain.
>
> On Wed, Nov 12, 2008 at 4:36 PM, Linn Renée Naper <linn.naper@ecgroup.no> wrote:
>
>> egen var=_n, by(group) will give me a variable counting from 1 til N within each group of the data.
>> BUT: how do I tell stata that the observations are double in the sense that I need a variable that repeats each number ones,
>> like this: 11 22 33 44.... instead of 1 2 3 4.....
>> I need this variable in order to collapse the data.
>
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```