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


From   "Lachenbruch, Peter" <[email protected]>
To   "[email protected]" <[email protected]>
Subject   RE: st: Cannot generate a dummy variable using if command
Date   Fri, 2 Aug 2013 20:56:42 +0000

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: [email protected] [[email protected]] on behalf of Joseph Kwan [[email protected]]
Sent: Friday, August 02, 2013 11:26 AM
To: [email protected]
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: [email protected] [[email protected]] on behalf of Joe Canner [[email protected]]
Sent: Friday, August 02, 2013 7:21 PM
To: [email protected]
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: [email protected] [mailto:[email protected]] On Behalf Of Sergiy Radyakin
Sent: Friday, August 02, 2013 2:14 PM
To: [email protected]
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 <[email protected]> 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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