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Re: st: RE: question on datatypes


From   "NEYMOTIN, FLORENCE" <neymotin@calmail.berkeley.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: question on datatypes
Date   Thu, 20 Oct 2005 05:40:42 -0700

that is a good idea. thanks for the help!!
florence

On Thu, 20 Oct 2005 10:25:08 +0100
 "Nick Cox" <n.j.cox@durham.ac.uk> wrote:
This is a frequent question on Statalist.
If you what are reading in, although it looks
like a standard numeric variable with a decimal
point, is really some kind of identifier or code, then I think by far the safest strategy is to read it in as a string variable and then do string manipulations on it. This can include removing the point.
Even if you read it in as -float- and then convert
to -long- it is all too likely that errors will
be introduced in the last digit or so.
As a thread yesterday advised, -search precision-
and look at the FAQs there mentioned. The underlying
issue is that computers are really doing calculations
in binary, not decimal. A massive amount of cleverness goes into
hiding this fact from the user, and even the programmer, but it is inescapable and on occasions can bite you.
Nick n.j.cox@durham.ac.uk
NEYMOTIN, FLORENCE


I have variables that are coded in as 2-3 digits and 6 decimal places after that, e.g. 150.089873 and I want to convert this to get rid of the decimal places so it looks like 150089873 but when I just multiply by 1000000 then it keeps storing it as a "float" display i.e. 1.5E8 and more than that, the last decimal places are actually INCORRECT in the new version...it will say 1.50089875 instead...which is INCORRECT. I am using Stata 8 and that is where this problem occurs. I was wondering what the easiest way is to change datatypes that something is input in so that it will not be a problem.
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