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Re: st: Inconsistent Result of generating variables


From   "Jitian Sheu" <jtsheu@bu.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   Re: st: Inconsistent Result of generating variables
Date   Fri, 9 Apr 2004 22:12:02 -0400

Hello,
What I meant is that this time, the result is "correct".
Both formula produce the same results.


Thanks.

Jitian
----- Original Message ----- 
From: "Richard Williams" <Richard.A.Williams.5@nd.edu>
To: <statalist@hsphsun2.harvard.edu>
Sent: Friday, April 09, 2004 10:08 PM
Subject: Re: st: Inconsistent Result of generating variables


> At 09:22 PM 4/9/2004 -0400, Jitian Sheu wrote:
> >Hello, Thank you very much.
> >Based on your explaination, I try to use: (`b21')^2 instead of using
> >`b21'^2.
> >Stata creates the same results.
>
> I hope you mean you got the same results as I did, not the same incorrect
> results you got earlier!  Anyway, here is the Stata FAQ I was thinking
of -
> "I coded 'a'2 and got the wrong sign. Why?"  See
>
> http://www.stata.com/support/faqs/lang/macpow.html
>
> The trick is that when you say,
>
> local b21=-0.25
>
> You naturally assume that Stata will think `b21' means "negative
> .25".  But, Stata actually interprets it as "minus .25".  Hence, with
> `b21'^2, exponentiation gets done first and then subtraction, leaving you
> with -.0625 rather than +.0625.
>
> The FAQ suggests two workarounds:
>
> * Use scalars instead of local macros, e.g.
>
> scalar b21 = -.25
>
> * Or, bind the macro in parentheses when taking powers, e.g
>
> (`b21')^2
>
> *
> *   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/
>

*
*   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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