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Re: st: is something wrong with fvvarlist "i(3 4).role"?
From
László Sándor <[email protected]>
To
[email protected]
Subject
Re: st: is something wrong with fvvarlist "i(3 4).role"?
Date
Tue, 13 Jul 2010 02:56:12 +0200
Thank you, Michael!
I acknowledge this behavior, but I find it strange (= not very
intuitive for most uses of this) and also somewhat contrary to the
manual's explanation (below). So I need to add another arbitrary level
just to be able to introduce the level indicators I originally
intended to? How clumsy...
Thanks again,
Laszlo
Selecting levels
You can select a range of levels -- a range of virtual variables -- by
using the i(numlist). operator.
Examples Description
--------------------------------------------------------------------
i2.cat a single indicator for cat==2
2.cat same as i2.cat
i(2 3 4).cat three indicators, cat==2, cat==3, and cat==4;
same as i2.cat i3.cat i4.cat
i(2/4).cat same as i(2 3 4).cat
2.cat#1.sex a single indicator that is 1 when cat==2 and
sex==1, and is 0 otherwise
i2.cat#i1.sex same as 2.cat#1.sex
--------------------------------------------------------------------
On Tue, Jul 13, 2010 at 2:21 AM, Michael N. Mitchell
<[email protected]> wrote:
> 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
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
>> * http://www.stata.com/support/statalist/faq
>> * http://www.ats.ucla.edu/stat/stata/
>
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
*
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