(PR#12742) Different result with different order of

Thank you for the prompt reply.

Do you know why does MS-Excel give result that I expected?

Thanks,

Kyun-Seop BAE
Email: kyunseop.bae at gmail.com


-----Original Message-----
From: Prof Brian Ripley [mailto:ripley at stats.ox.ac.uk]
Sent: Monday, September 08, 2008 1:53 AM
To: kyunseop.bae at gmail.com
Cc: R-bugs at r-project.org
Subject: Re: [Rd] (PR#12742) Different result with different order of
binding

FAQ 7.31 strikes again.

This is expected: you cannot do exact arithmetic on a binary computer if
some of the quantities involved are not binary fractions (e.g. 1.3)

See also the warning in ?`==`: identical() is equally inappropiate for
computed numerical quantities.

On Mon, 8 Sep 2008, kyunseop.bae at gmail.com wrote:

Full_Name: Kyun-Seop Bae
Version: 2.7.2
OS: MS-Windows XP SP2
Submission from: (NULL) (148.168.40.4)


# Script that I used

rm(list=objects())
objects()

WT <- 91
AGE <- 41
SCR <- 1.3

CCL1 <- (140-AGE) * WT / (72 * SCR)
CCL2 <- (140-AGE) * WT / 72 / SCR

CCL1
CCL2

identical(CCL1, CCL2)
identical(CCL1, 96.25)
identical(CCL2, 96.25)

CCL1*10 + 0.5
CCL2*10 + 0.5

floor(CCL1*10 + 0.5)
floor(CCL2*10 + 0.5)

as.integer(CCL1*10 + 0.5)
as.integer(CCL2*10 + 0.5)


# Same with multiplied WT
# Same in S-Plus Enterprise Developer Version 7.0.6 for Microsoft Windows

:

2005
# But these are accurate in MS-Excel.

Unlikely, more likely you don't have identical() to test bit-level
equality.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595