Nick Cox
> Kostova Deliana (HXX1DAK)
> >
> > I ran into the following small problem that, I think, has
> > to do with storage
> > types, but I'm not sure how to solve it...
> >
> > Suppose we want to calculate the product of -.1796042 and
> > 4.752947, so we
> > type:
> > display -.1796042^4.752947
> > and we get
> > -.00028563
> >
> > However, if we have variable X= -.1796042 and variable
> > Y=4.752947, and we
> > type
> > gen Z=X*Y, Stata will generate Z=. even though Z should be
> > -.00028563.
> >
> > I know this has to do with storage types, so i tried
> > gen double Z=X*Y, but this still produces a missing variable...
>
> What do you want, power ^ or product * ?
>
> I get with StataSE 8
>
> . di -.1796042^4.752947
> -.00028563
>
> . di -.1796042*4.752947
> -.85364924
>
> . clear
>
> . set obs 1
> obs was 0, now 1
>
> . gen power = -.1796042^4.752947
>
> . gen product = -.1796042*4.752947
>
> . l
>
> +-----------------------+
> | power product |
> |-----------------------|
> 1. | -.0002856 -.8536493 |
> +-----------------------+
When I say power, I mean "negated power".
Stata won't calculate
(negative number)^(non-integer power)
due to its narrow view of arithmetic.
It interprets
-.1796042^4.752947
as
-(.1796042^4.752947)
as a consequence of its precedence rules
(powering before negation).
Nick
[email protected]
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