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Re: st: Dropping min of two consecutive observations


From   "Alan Neustadtl" <alan.neustadtl@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Dropping min of two consecutive observations
Date   Thu, 13 Nov 2008 16:42:48 -0500

If you sort the data by id and then by month I think your code will
work.  Look at the following example based on your data:

***** Stata Example Begin *****
clear

input byte id byte value  byte month
1  25        12
1  22         8
2  30         9
3  28         8
3  24         6
end

list

sort id month
list

drop if id==id[_n-1]
list

***** Stata Example End *****


Best,
Alan

On Thu, Nov 13, 2008 at 4:33 PM, Rijo John <rmjohn@gmail.com> wrote:
> Dear Statalist,
>
>  I have some repeated observations that I need to drop. I have defined
> a unique ID variable. There are two other variables "value" and
> "month" for these IDs.
>
> Example data.
>
> ID Value  month
> 1  25        12
> 1  22         8
> 2  30         9
> 3  28         8
> 3  24         6
>
>
> Only few IDs are repeated in the actual data.
>
> Basically I need to retain only one value per ID. If I do "drop if
> ID==ID[_n-1]" after sorting the IDs it could drop any of the values.
> But I want the data to retain those values where in month takes the
> highest value when I am dropping ID==ID[_n-1].  Something like
>
> drop min(month, month[_n-1]) if ID==ID[_n-1] is what I am looking for.
> However, I cant use such time series operators with min function. Any
> thoughts?
>
> Regards,
> Rijo.
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