[R-SIG-Mac] Unexpected output from round()

[Duncan Murdoch]

On 12/06/2015 8:53 PM, John Maindonald wrote:
> I cannot reproduce it (R version 3.2.0 Patched (2015-04-19 r68206)) in a terminal window:

If you set options(digits=16) you'll get it.  It's just FAQ 7.31, and
the fact that R only stores 15 or 16 digit accuracy.

Duncan Murdoch

> 
>> dput(pi)
> 3.14159265358979
>> round(dput(pi),2)
> 3.14159265358979
> [1] 3.14
>> Cl <- c(82.9888290534313, 100.544763749464)
>> dput(Cl)
> c(82.9888290534313, 100.544763749464)
>> round(dput(Cl),2)
> c(82.9888290534313, 100.544763749464)
> [1]  82.99 100.54
>> sessionInfo()
> R version 3.2.0 Patched (2015-04-19 r68206)
> Platform: x86_64-apple-darwin13.4.0 (64-bit)
> Running under: OS X 10.10.3 (Yosemite)
> 
> locale:
> [1] en_NZ.UTF-8/en_NZ.UTF-8/en_NZ.UTF-8/C/en_NZ.UTF-8/en_NZ.UTF-8
> 
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base  
> 
> John Maindonald             email: john.maindonald at anu.edu.au
> 
>> On 13/06/2015, at 12:39, Dennis Fisher <fisher at plessthan.com> wrote:
>>
>> R 3.2.0
>> OS X
>>
>> Colleagues
>>
>> I received unexpected output from a command issued in a terminal window:
>>
>>> dput(CI)
>> c(82.9888290534313, 100.544763749464)
>>
>>> round(dput(CI), 2)
>> c(82.9888290534313, 100.544763749464)
>> [1]  82.98999999999999 100.54000000000001
>>
>> I expected the result of the second command to be:
>> 	82.99   100.54
>>
>> Interesting, the problem also occurs if I round to 5 or 8 digits.  
>>
>> Of note, the problem does NOT occur in R GUI or in Windows.
>>
>> I am aware of FAQ 7.31 (Why doesn’t R think these numbers are equal?) but I don’t see how this could be manifestation of that issue.
>>
>> I am curious as to the explanation of this issue.
>>
>> Dennis
>>
>>
>> Dennis Fisher MD
>> P < (The "P Less Than" Company)
>> Phone: 1-866-PLessThan (1-866-753-7784)
>> Fax: 1-866-PLessThan (1-866-753-7784)
>> www.PLessThan.com
>>
>> _______________________________________________
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>> R-SIG-Mac at r-project.org
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> 
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