[Bioc-devel] simple question about floor

[Steven McKinney]

Yes, floating point issue.

See e.g. 

http://cran.r-project.org/doc/FAQ/R-FAQ.html
7.31 Why doesn't R think these numbers are equal?


> options(digits = 22)
> 29/50
[1] 0.579999999999999960032
> 29/50 * 50
[1] 28.99999999999999644729
> 29*50/50
[1] 29.00000000000000000000
> .58 * 50
[1] 28.99999999999999644729
> floor(28.999999)
[1] 28.00000000000000000000
> floor(29.000000)
[1] 29.00000000000000000000
> 



Steven McKinney

Statistician
Molecular Oncology and Breast Cancer Program
British Columbia Cancer Research Centre



> -----Original Message-----
> From: bioc-devel-bounces at r-project.org [mailto:bioc-devel-bounces at r-
> project.org] On Behalf Of Ou, Jianhong
> Sent: December-19-13 1:53 PM
> To: bioc-devel at r-project.org
> Subject: [Bioc-devel] simple question about floor
> 
> Hi all,
> 
> Maybe this is not a bioconductor question but R. However, I feel this is
> very interesting.
> 
> I tried
> 
> > floor(29/50*50)
> [1] 28
> > floor(29*50/50)
> [1] 29
> 
> Is this a floating-point problem? How could we explain this?
> 
> Yours sincerely,
> 
> Jianhong Ou
> 
> LRB 670A
> Program in Gene Function and Expression
> 364 Plantation Street Worcester,
> MA 01605
> 
> 	[[alternative HTML version deleted]]
> 
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