# st: AW: Splitting panel in 3 groups: gen byte

 From "Martin Weiss" <[email protected]> To <[email protected]> Subject st: AW: Splitting panel in 3 groups: gen byte Date Wed, 17 Jun 2009 10:25:56 +0200

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So John, just to be sure: The random numbers from the uniform distribution
are -generate-d to determine a random sort order, and the -gen byte-
statement uses the fact that the in-built _n and _N are calculated within
groups determined by the by groups. The condition passed to the -cond()-
function says that the data which has been sorted randomly should now be
assigned values for the group identifier "group", "1" for the first half (
where the running number _n is smaller/equal to half the number of
observations in a by group), and 2 for the remainder...

HTH
Martin

-----Ursprüngliche Nachricht-----
Von: [email protected]
[mailto:[email protected]] Im Auftrag von John Antonakis
Gesendet: Mittwoch, 17. Juni 2009 09:47
An: [email protected]
Betreff: st: Splitting panel in 3 groups: gen byte

Hi:

Martin recently helped with me with some code, to randomly split panel
data equally into two groups (which I then collapsed afterwards).

I am trying to understand the code regarding the split. My panel
identifier is "i".

gen random=runiform()
sort i random
by i: gen byte group=cond(_n<=_N/2,1,2)

So, how to I split into 3 groups or 4 groups?  I am not sure what the
"gen byte" command does and how the numbers 2,1,2 relate to the command.

John.

--
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