Re: st: Generating a list with combinations' counts and their description

["MA V" <ma_v@hotmail.com>]

Thanks to all.  The -groups- command was exactly what I needed!

> From: n j cox <n.j.cox@durham.ac.uk>
> Reply-To: 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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