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Re: st: is something wrong with fvvarlist "i(3 4).role"?


From   "Michael N. Mitchell" <Michael.Norman.Mitchell@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: is something wrong with fvvarlist "i(3 4).role"?
Date   Mon, 12 Jul 2010 17:21:55 -0700

Greetings

The trick is that the -i.- is creating a reference group, so in your example group 3 is the reference group. Here are some examples using the -auto- dataset.

. sysuse auto
(1978 Automobile Data)

* group 1 is the reference, groups 2-5 are shown
. summ   i.rep78

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
       rep78 |
          2  |        69     .115942    .3225009          0          1
          3  |        69    .4347826    .4993602          0          1
          4  |        69    .2608696    .4423259          0          1
          5  |        69    .1594203    .3687494          0          1

* group 1 is the reference, groups 2-5 are shown
. summ   i(1/5).rep78

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
       rep78 |
          2  |        69     .115942    .3225009          0          1
          3  |        69    .4347826    .4993602          0          1
          4  |        69    .2608696    .4423259          0          1
          5  |        69    .1594203    .3687494          0          1

* group 1 is the reference, groups 2-4 are shown
. summ   i(1/4).rep78

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
       rep78 |
          2  |        69     .115942    .3225009          0          1
          3  |        69    .4347826    .4993602          0          1
          4  |        69    .2608696    .4423259          0          1

* group 1 is the reference, groups 2-3 are shown
. summ   i(1/3).rep78

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
       rep78 |
          2  |        69     .115942    .3225009          0          1
          3  |        69    .4347826    .4993602          0          1

* group 1 is the reference, group 2 is shown
. summ   i(1/2).rep78

    Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
     2.rep78 |        69     .115942    .3225009          0          1


I hope that helps.

Michael N. Mitchell
Data Management Using Stata      - http://www.stata.com/bookstore/dmus.html
A Visual Guide to Stata Graphics - http://www.stata.com/bookstore/vgsg.html
Stata tidbit of the week         - http://www.MichaelNormanMitchell.com



On 2010-07-12 4.21 PM, László Sándor wrote:
Hi all,
I think I have a straightforward question in the subject line.

I use the up-to-date Stata on a mac. The factor variable handling does
not work as promised in the manual (cf. -h fvvarlist-). See the most
striking, simple example below. Or am I missing the obvious?

Thank you,

Laszlo



. sum i(3 4).role

     Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
       4.role |       747    .2503347     .433496          0          1

. sum i(3/4).role

     Variable |       Obs        Mean    Std. Dev.       Min        Max
-------------+--------------------------------------------------------
       4.role |       747    .2503347     .433496          0          1
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