Re: repost: -cond()- function

[Michel Camus <mcamus@videotron.ca>]

My previous message was tainted by my new Year's hangover. Sorry about 
that.

How is your original variable "chol" coded? How are the "missing values" 
of "chol" coded, more specifically?

".gen cholcat = cond(chol,0,1,9)"   codes "cholcat" properly if  "chol" 
has missing values coded as "."
 ... but it does not code "9" if "chol" has "missing values" coded as "9".
The function used is described in Stata as : "cond(x,a,b,c):  a if x 
evaluates to true (not 0), b if x evaluates to false (0), and c if x 
evaluates to missing (.)".
Your expression would not evaluate "chol==9" as "missing" but as "not 
1", that is as "0".
I don't know if this helps. Hope it does.

Michel
========
Michel Camus wrote:


> I experience the same "problem" as you do, Paul.
> I believe it has to do with "binary logic". The logical condition 
> ("chol") always evaluates to 0 or 1, and nothing else,  it  never 
> evaluates to "9" even if the original variable does have "9" as one 
> value. The same happens even if your missing values in "chol" were 
> already coded as "." See 
> http://www.stata.com/support/faqs/data/values.html  by W. Gould on 
> "Logical expressions and missing values". The way to have missing 
> values is tocondition your expression as follows :               .gen 
> cholcat = cond(chol,0,1) if chol != 9
> Then you would still have to replace the missing (".") by "9" however 
> if that is what you want.
>
> Michel Camus
> ===============================
> VISINTAINER PAUL wrote:
>
>
> > I am reposting this message:
> >  
> > I have an integer variable that I would like to collapse into a 
> > dichotomous variable. Using the following statement:
> >
> >      .gen cholcat = cond(chol,0,1,9)
> >
> > produces the same output as:
> >
> >     .gen cholcat = cond(chol,0,1)
> >
> > The first statement continues to recode "missings" as 1, not 9.  In 
> > order to capture the missings appropriately, I have to follow each 
> > -cond()- statement with a -replace- command.
> >
> >
> > Am I using the -cond()- function appropriately?
> >
> > Thanks,
> >
> > paul visintainer
> >
> > *
> > *   For searches and help try:
> > *   http://www.stata.com/support/faqs/res/findit.html
> > *   http://www.stata.com/support/statalist/faq
> > *   http://www.ats.ucla.edu/stat/stata/
> >
> >  
--

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Michel Camus, Ph.D.

Épidémiologue, Div. Biostatistique et épidémiologie, DGSESC, Santé Canada

Epidemiologist, Biostatistics and Epidemiology Div., HECSB, Health Canada

Courriel / e-mail : mcamus@videotron.ca <mailto:mcamus@videotron.ca>

Téléphone / phone     :    (514) 850-0157

Télécopieur / fax        :    (514) 850-0836

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*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/