[Bioc-devel] simple question about floor

[Ou, Jianhong]

Thanks Steven. Very clear.

Yours sincerely,

Jianhong Ou

LRB 670A
Program in Gene Function and Expression
364 Plantation Street Worcester,
MA 01605




On 12/19/13 5:54 PM, "Steven McKinney" <smckinney at bccrc.ca> wrote:

>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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