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Re: st: How to identify two consequtives values of a variable


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: How to identify two consequtives values of a variable
Date   Fri, 22 Jul 2011 13:12:41 -0500

. gen previous = x[_n-1] if abs(x[_n-1])
. replace previous = previous[_n-1] if missing(previous)
. gen y = x == 1 & previous ==1


Nick

On Fri, Jul 22, 2011 at 12:06 PM, Pablo.CARVALLO <pablocepal@gmail.com> wrote:
> Hi Statalist,
>
> I create a variable x which states a local max (1), a local min(-1),
> and 0 in other case. If x==1, the following value may be 0 or -1, but
> it cannot be 1 again. For example, an 'ideal' x may be:
>
> x
> --
> 0
> 0
> 1
> 0
> 0
> 0
> 0
> -1
> 0
> 0
> 1
> -1
> 0
> 0
> 0
> 1
>
> But I have something like this:
>
> x
> --
> 0
> 0
> 1
> 0
> 0
> 0
> 0
> 1 ----> this value is wrong, because previous x different from 0 was 1.
> 0
> 0
> -1
> 1
> 0
> 0
> 0
> -1
>
> I need a variable 'y' which tells me when x takes this wrong values:
>
> x     y
> ---------
> 0     0
> 0     0
> 1     0
> 0     0
> 0     0
> 0     0
> 0     0
> 1     1 ---> y==1
> 0     0
> 0     0
> -1    0
> 1     0
> 0     0
> 0     0
> 0     0
> -1    0
>

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