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st: Re: Tab and Matcell


From   "Marcela Perticara" <perticara@econ.tamu.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: Re: Tab and Matcell
Date   Thu, 13 Jun 2002 09:29:21 -0500

If the onlly thing you want is to get the counts for each manuf-class
combination, you could general a two-way table

tab manuf class, matcell(classmat)


and the matrix classmat will contain the counts for each manuf-class
combinations.




----- Original Message -----
From: "Fraser, Steven" <SFraser@coba.usf.edu>
To: "Statalist (E-mail)" <statalist@hsphsun2.harvard.edu>
Sent: Thursday, June 13, 2002 8:48 AM
Subject: st: Tab and Matcell


> Dear Statalist:
>
> I am having a problem implementing matrix operations within the 'tab'
> command.  Using a variation of the familiar car example, assume I have the
> following dataset:
>
> Manuf Model Class MPG
> ford explorer SUV 12
> ford expedition SUV 10
> ford focus compact 34
> dodge durango SUV 16
> gm tahoe SUV 15
>
> Assume I have hundreds of automobiles (cars, trucks, and SUVs).  I am
trying
> to develop a focus measure (a Herfandahl index) that captures the focus of
> the manufacturer.  For example, GM (with all the GM lines) would probably
> have a lower focus measure, while Volkswagon, which doesn't make any
trucks
> or SUVs, would have a higher focus measure.  What I need is the frequency
of
> each class which will be different for each manufacturer.
>
> My approach has been
>
> sort manuf
> by manuf: tab class, matcell(classmat)
> mat list classmat
>
> Part 1 of my question:  The resulting matrix is only for the last 'manuf'.
> It will not allow "by:"  Can I incorporate as part of a loop?
> Part 2 of my question:  I then need to access the variables and perform
> calculations.  Would it be possible to put all the results in one matrix?
>
> Thanks for the assist..SF
>
>
> Steve Fraser
> Univ of South Florida
>
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