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Re: st: variables precision


From   Kyle Hood <[email protected]>
To   [email protected]
Subject   Re: st: variables precision
Date   Wed, 4 Apr 2007 20:10:48 -0400 (EDT)

Another possibility would be to generate a variable that is the
difference between the two variables,

gen z = y - x

and count if z is small, e.g.,

count if z > 0.0000001

This won't be perfect, but as long as the variables are generated at random, there's only a tiny chance that they'll fall within such a small bound randomly.

Kyle


On Thu, 5 Apr 2007, sara borelli wrote:


I tried but after converting to float stata still
reports that for some observations the inequality is
satisfied , and I do not understand why...

--- Kyle Hood <[email protected]> ha scritto:

couldn't you just recast both as floats (generating
a new pair of
variables), do the operation, and then, if you wish,
delete the new
variables?

something like this

gen float xf = x
gen float yf = y
gen z = xf < yf
drop xf yf



On Thu, 5 Apr 2007, sara borelli wrote:

Dear Statalist members

I know this is a precision question already posted
in
the past, but I have difficulties to understand
the
right way to go even after looking at the archives
of
statalist

I have two variables:
 x        y
17.68    17.68
15.56    15.56
19.27    19.27
5.3      5.3

If I write 'count if x<y' stata says that all
observations satisfy this inequality, when in fact
the
values 'look' the same. I think this has to do
with the fact that x is stored as double, while y
is
stored as float. Is there any way I can say stata
to
read the values as they "appear" and thus
performing
calculations correctly (in this case I would need
stata say that there are zero observations for
which
x<y)? I am sorry to repeat this question, but any
suggestion would be really appreciated

thanks
Sara






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