From a215020@agate.fmr.com  Tue Oct 23 00:15:39 2001
From: a215020@agate.fmr.com (a215020@agate.fmr.com)
Date: Tue, 23 Oct 2001 01:15:39 +0200 (MET DST)
Subject: [Rd] round() doesn't (PR#1139)
Message-ID: <200110222315.BAA12002@pubhealth.ku.dk>

R> round(100000/3, -2) - 33300
   [1] -7.275958e-12

I would have hoped for 0.  The problem seems to be specifically for negative
"digits".  This is in 1.3.1 on Solaris 2.6 (full description at bottom).

[Apologies for making everyone read this 3 times; my bug.report() burped.]

Peter Dalgaard <p.dalgaard@biostat.ku.dk> says the problem is in fround.c,
which reads in part:
    pow10 = R_pow_di(10., dig)
    ...
    return sgn * (intx + R_rint(x * pow10) / pow10);
and (says Peter),
> the problem is most likely that pow10 (== 1/100) has no finite binary
> representation. Patches are welcome...

I'm not up to patching C code, but I will say that a workaround is:
R> round(round(100000/3, -2)) - 33300
   [1] 0
and a smarter C-programmer could probably implement this concept:
if digits < 0, force the final result to an integer.

			-- David Brahm (brahm@alum.mit.edu)

Version:
 platform = sparc-sun-solaris2.6
 arch = sparc
 os = solaris2.6
 system = sparc, solaris2.6
 status = 
 major = 1
 minor = 3.0
 year = 2001
 month = 06
 day = 22
 language = R

Search Path:
 .GlobalEnv, package:misc, package:io, package:arrays, package:ls1, package:db, package:ts, package:ctest, Autoloads, package:base

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[Rd] round() doesn't (PR#1139)
a215020@agate.fmr.com