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Re: st: comparing variables across time
From
Nick Cox <[email protected]>
To
[email protected]
Subject
Re: st: comparing variables across time
Date
Mon, 30 Apr 2012 10:26:32 +0100
I am not sure I follow this as your question stresses joint occurrence
in one place but focus on individual occurrence in another. But
bysort P1 P2 (year) : gen seq = _n
tags successive joint occurrences of -P1- and -P2-. Then
. list P1 P2 if seq == 1 & year == 1996
shows joint occurrences that first appeared in 1996 and
. count if seq == 1 & year == 1996
counts them.
On Mon, Apr 30, 2012 at 10:15 AM, Navid Asgari <[email protected]> wrote:
> I want to do a pair wise comparison of several variables across different years. I would like to know how many new characters under P1 and P2 (together)exists in year 1996 that did not exists in year 1995.
>
>
>
> The dataset looks like this:
>
> Year P1 P2
> -------- ------- ------
> 1995 A B
> 1995 A C
> 1995 D A
> 1995 E A
> 1996 B A
> 1996 A M
> 1996 A H
> 1996 A C
>
>
> So the code should show "2", since character M and H exist under P1 and P2 in the year 1996, but not in 1995.
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