Re: st: Identify Categorical/Dichotomous and Continuous Variables

[Steven Samuels <sjhsamuels@earthlink.net>]

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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