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Re: st: Confirming whether a variable is binary or continuous


From   Eric Booth <eric.a.booth@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Confirming whether a variable is binary or continuous
Date   Fri, 16 Mar 2012 16:28:30 -0500

<>

One way is to -tabulate- the var and then use stored value in r(r) to tell how many values it has.  You could also grab values from the user-written packages -egenmore- (form SJ, see the nvals() fcn) and -distinct- (from SSC)


Example:

*********

sysuse auto, clear

ds, has(type numeric)
foreach x in `r(varlist)' {
quietly tabulate `x'
if r(r) == 2 di in red `"`x' is binary"'
if r(r)!=2  di "`x'  is not binary"
}
*********

- Eric

__
Eric A. Booth
Public Policy Research Institute 
Texas A&M University
ebooth@ppri.tamu.edu
+979.845.6754

On Mar 16, 2012, at 4:18 PM, Bert Jung wrote:

> Dear Statalisters,
> 
> I am writing a short program to make a balance table that compares
> covariates across a treatment and control group.  I am looking for a
> way to confirm whether a variable is binary in order to use -prtest-
> for proportions rather than -ttest- for continous variables.
> 
> One option is to check the actual data values and do -prtest- if there
> are only 0's and 1's.  But a continuous but rare outcome could
> accidentally also take these values, e.g. the number of
> hospitalizations in the past 3 months.
> 
> Is there a safer way to confirm that a variable is binary?
> 
> Thanks for any pointers,
> Bert
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