
From  "MA V" <ma_v@hotmail.com> 
To  statalist@hsphsun2.harvard.edu 
Subject  Re: st: Generating a list with combinations' counts and their description 
Date  Wed, 23 May 2007 17:13:50 +0000 
Thanks to all. The groups command was exactly what I needed!
From: n j cox <n.j.cox@durham.ac.uk>_________________________________________________________________
ReplyTo: statalist@hsphsun2.harvard.edu
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Generating a list with combinations' counts and their description
Date: Wed, 23 May 2007 12:39:25 +0100
Svend and Maarten are both right. Deep down, their answer
is the same, as groups is based on exactly the Stata
logic that Maarten exposes, plus bells and whistles.
Your original idea was good too.
egen group = group(var1 var2 var3), label
tab group
will do what you want as well. The label option
is crucial to get close to the display you want.
For examples more complicated, groups has more
handles.
Nick
n.j.cox@durham.ac.uk
Svend Juul
==========
Nick Cox made the groups command; it does what you want. Get it by:
ssc install groups
Maarten Buis
============
A rather blunt solution is shown below:
* begin example 
drop _all
input obs var1 var2 var3
1 2 2 1
2 2 2 1
3 1 2 3
4 3 3 3
end
preserve
drop if missing(var1, var2, var3)
bys var1 var2 var3: gen N = _N
bys var1 var2 var3: keep if _n == 1
list var1 var2 var3 N
restore
* end example 
(For more on how to use examples I sent to the Statalist, see
http://home.fsw.vu.nl/m.buis/stata/exampleFAQ.html )
V MA
====
I have 3 variables that can take the values 1 up to 3 and the data looks
something like this
obs var1 var2 var3
1 2 2 1
2 2 2 1
3 1 2 3
4 3 3 3
I would like to obtain a table that says how many observations I have of
each existing combination. But I would like this table to have a
"description" for each of the combinations. i.e. the resulting table
would be something like this:
var1 var2 var3 count
1 2 3 1
2 2 1 2
3 3 3 1
Note also that the lines in the table are ordered by the values of var1,
var2 and var3.
*
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