RE: st: Cannot generate a dummy variable using if command

["Lachenbruch, Peter" <Peter.Lachenbruch@oregonstate.edu>]

it's been my experience (so far) that when i'msure there's an error in stata, the usual error has been in me.  The program is really outstanding.  We do hear of a few problems on a new release, but my usage is so confined to common issues that they rarely affect me.  

Peter A. Lachenbruch,
Professor (retired)
________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] on behalf of Joseph Kwan [JXK180@bham.ac.uk]
Sent: Friday, August 02, 2013 11:26 AM
To: statalist@hsphsun2.harvard.edu
Subject: RE: st: Cannot generate a dummy variable using if command

Thanks Sergiy and Joe. I just tried and it worked. I get it now. It is a relief to know there is nothing wrong with the program :)

Joseph
________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] on behalf of Joe Canner [jcanner1@jhmi.edu]
Sent: Friday, August 02, 2013 7:21 PM
To: statalist@hsphsun2.harvard.edu
Subject: RE: st: Cannot generate a dummy variable using if command

To elaborate a bit on what Sergiy said...

The reason you need to add "!missing(age)" (or similar) to your statement is that a missing value is the largest value there is (i.e., the highest number possible for that data type, plus one).  Thus, a missing value for age will always satisfy the condition "if age>25"

This is in contrast to SAS, for example, where missing values are the lowest value there is (i.e., the lowest number possible minus one).

Regards,
Joe

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Sergiy Radyakin
Sent: Friday, August 02, 2013 2:14 PM
To: statalist@hsphsun2.harvard.edu
Subject: Re: st: Cannot generate a dummy variable using if command

There is nothing wrong.
Type summarize age and look at the min age reported.

A simpler and more robust version is something like:
gen old=age>25 if !missing(age)
Finally note that in nlsw88 dataset (if you are using it) there are no individuals younger than 34.
Best, Sergiy

On Fri, Aug 2, 2013 at 2:05 PM, Joseph Kwan <JXK180@bham.ac.uk> wrote:
> I would like to generate a variable for people older than 25 years
> old,
>
> so I use
>
> gen old=1  if age>25
>
> but then Stata returns with an old dummy variable with all 1 for all observations.
>
> I checked the syntax and I do not know what is wrong.
>
> Is Stata known to have faults like that?
>
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