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Re: st: Identify Categorical/Dichotomous and Continuous Variables


From   fgallo@wnec.edu
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Identify Categorical/Dichotomous and Continuous Variables
Date   Sun, 5 Oct 2008 19:28:38 -0400

Thank you all very much for responding with your thoughts and suggestions.

Best,
Frank


On Sun 05/10/08  3:26 PM , Steven Samuels sjhsamuels@earthlink.net sent:
> Agreed.
> 
> 
> 
> -Steve
> 
> On Oct 5, 2008, at 1:11 PM, Nick Cox wrote:
> 
> 
> 
> > Good advice, but to repeat for Frank and any others
> puzzled: Stata  
> > does
> 
> > not think of such variables as nominal, indicator,
> etc. If  
> > something is
> 
> > (say) coded 0, 1 or missing then any user is
> perfectly entitled to  
> > think
> 
> > of it as an indicator/dummy, etc., but Stata does
> not think that way.
> > It's in your mind, not Stata's.
> 
> >
> 
> > Nick
> 
> > n.j.cox@
> durham.ac.uk
> >
> 
> > Steven Samuels
> 
> >
> 
> > To turn any variable in Stata into a nominal
> variable, you create
> > indicator variables.  This is what SPSS does when
> you use a
> > categorical variable as a predictor in regression.
> There are two ways
> > of doing this in Stata: a) -xi- or b) -tab- with
> the -gen()- option.
> > See http://www.ats.ucla.edu/stat/Stata/webbooks/reg/chapter3/
> > statareg3.htm   Section 3.3 for some examples.
> 
> >
> 
> > On Oct 5, 2008, at 12:33 PM, Nick Cox wrote:
> 
> >
> 
> >> This is not quite true. In particular, -anova- has
> an idea of the
> >> distinction. If you specify that a variable is
> categorical or
> >> continuous, or imply that by default, -anova-
> takes action
> >> accordingly.
> 
> >>
> 
> >> But in general, as others have emphasised or
> implied, Stata puts the
> >> onus on users to decide how they want variables to
> be treated. If you
> >> want -foreign- in the auto data to be a binary
> response for -logit-,
> >> that's fine. If you want to average it with
> -summarize-, that's fine
> >> too. Sometimes, Stata will refuse to do something
> on principle; more
> >> usually, it assumes that you are smart enough to
> know what you  
> >> want to
> 
> >> do.
> 
> >>
> 
> >> # of distinct values is, as Svend will agree, a
> criterion to be used
> >> circumspectly. I often deal with rainfall data
> usually measured by
> >> convention to a resolution of 0.1 mm. I bet that
> the number of
> >> distinct
> 
> >> values met in practice is fewer than that in the
> typical
> >> classifications
> 
> >> of death, disease or economic activity.
> 
> >>
> 
> >> Nick
> 
> >> n.j.cox@
> durham.ac.uk
> >>
> 
> >> Svend Juul
> 
> >>
> 
> >> As Martin responded: Stata has no formal
> distinction between
> >> continuous and categorical numeric variables.
> However, the
> >> command
> 
> >>
> 
> >>     codebook, compact
> 
> >>
> 
> >> may tell you what you want. The -Unique- column
> tells you
> >> how many "unique" (meaning different) values each
> variable
> >> has.
> 
> >>
> 
> >> Frank
> 
> >>
> 
> >> I am new to Stata: moved from SPSS a week ago. I
> am hoping
> >> that someone can help me with what I imagine is a
> simple
> >> issue. I saved an SPSS file as a Stata one. I am
> working
> >> my way through the user guide and the data
> management
> >> manual, but I am having difficulty with confirming
> whether
> >> Stata recognizes variables as continuous (or
> scale) or
> >> categorical/dichotomous (or nominal). In SPSS, you
> can
> >> easily identify whether the type of measure is a
> scale,
> >> nominal, or string with its drop down menu in the
> variable
> >> view. It would be a great help, and I would
> appreciate it
> >> very much if someone would tell me the method to
> confirm
> >> the data type for categorical/dichotomous and for
> 
> >> continuous variables? Thank you.
> 
> >
> 
> > *
> 
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> 
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> > *   http://www.ats.ucla.edu/stat/stata/
> 
> 
> *
> 
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> 
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> 
> 
> 
> 




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