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Re: st: Stata cannot do math?


From   Conor Hughes <cbhughes@uchicago.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Stata cannot do math?
Date   Wed, 18 May 2011 19:20:57 -0500

Hi,
Stata can certainly do math, just not quite the same math you're used
to.  This is an issue of floating point arithmetic.  For example,
replace
count a == 100.1
in your code with
count a == float(100.1)

Click through the FAQ a bit, maybe starting here
http://www.stata.com/support/faqs/data/float.html, as well as any
introductory numerical analysis textbook to get a better idea of how
computer arithmetic works.

- Conor

On Wed, May 18, 2011 at 6:44 PM, Yu Xue <snowrain@gmail.com> wrote:
>
> Hi All,
>
> This may be a stupid question. Here are the command and Stata output:
>
> .set obs 50
> .gen a=100.1
> .count if a==100.1
> 0
> .tab a
> 100.1
> .sum a
> variable  obs  mean  s.d.  min    max
> a            50    100.1  0    100.1  100.1
> .gen b=a-100
> .tab b
> 0.0999985
>
> So, Stata shows that a is equal to 100.1, but actually, it is equal to
> 100.0999985....
>
> Can anyone explain to me what this is? Do I have to set precision when
> I do math in Stata? How to set precision?
> Thanks!
>
> Yu
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