R help - Feb 2005 - round() - strange results

Hello,
 
  I found that round() does not behave as I expected.
  Have you had similar experience as following?
 
> x<-seq(0.5,10.5,by=1)
> x
 [1]  0.5  1.5  2.5  3.5  4.5  5.5  6.5  7.5  8.5  9.5
10.5
> round(x)
 [1]  0  2  2  4  4  6  6  8  8 10 10
> cbind(x,round(x))
         x   
 [1,]  0.5  0
 [2,]  1.5  2
 [3,]  2.5  2
 [4,]  3.5  4
 [5,]  4.5  4
 [6,]  5.5  6
 [7,]  6.5  6
 [8,]  7.5  8
 [9,]  8.5  8
[10,]  9.5 10
[11,] 10.5 10

 
  Is this a well-known bug?
 
Thanks in advance,
 
 
Dongseok Choi, Ph.D.
Assistant Professor
Division of Biostatistics
Department of Public Health & Preventive Medicine
Oregon Health & Science University
3181 SW Sam Jackson Park Road, CB-669
Portland, OR 97239-3098
TEL) 503-494-5336
FAX) 503-494-4981
choid@ohsu.edu

	[[alternative HTML version deleted]]

This in NOT a bug.  It is a convention (the IEEE standard).
Read the help on round().  I.e. RTFM.

			cheers,

				Rolf Turner
				rolf at math.unb.ca

?round

'round' rounds the values in its first argument to the specified
number of decimal places (default 0). Note that for rounding off a
5, the IEEE standard is used, "_go to the even digit_". Therefore
'round(0.5)' is '0' and 'round(-1.5)' is '-2'.

Dongseok Choi wrote:
> Hello,
>  
>   I found that round() does not behave as I expected.
>   Have you had similar experience as following?
>  
> 
>>x<-seq(0.5,10.5,by=1)
>>x
> 
>  [1]  0.5  1.5  2.5  3.5  4.5  5.5  6.5  7.5  8.5  9.5 10.5
> 
>>round(x)
> 
>  [1]  0  2  2  4  4  6  6  8  8 10 10
> 
>>cbind(x,round(x))
> 
>          x   
>  [1,]  0.5  0
>  [2,]  1.5  2
>  [3,]  2.5  2
>  [4,]  3.5  4
>  [5,]  4.5  4
>  [6,]  5.5  6
>  [7,]  6.5  6
>  [8,]  7.5  8
>  [9,]  8.5  8
> [10,]  9.5 10
> [11,] 10.5 10
> 
>  
>   Is this a well-known bug?
>  
> Thanks in advance,
>  
>  
> Dongseok Choi, Ph.D.
> Assistant Professor
> Division of Biostatistics
> Department of Public Health & Preventive Medicine
> Oregon Health & Science University
> 3181 SW Sam Jackson Park Road, CB-669
> Portland, OR 97239-3098
> TEL) 503-494-5336
> FAX) 503-494-4981
> choid at ohsu.edu
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> 
-- 
Chuck Cleland, Ph.D.
NDRI, Inc.
71 West 23rd Street, 8th floor
New York, NY 10010
tel: (212) 845-4495 (Tu, Th)
tel: (732) 452-1424 (M, W, F)
fax: (917) 438-0894

Dongseok Choi wrote:
> Hello,
>  
>   I found that round() does not behave as I expected.
>   Have you had similar experience as following?
You have found the DOCUMENTED "round to even" rule, hence not a bug...

Uwe Ligges
> 
>>x<-seq(0.5,10.5,by=1)
>>x
> 
>  [1]  0.5  1.5  2.5  3.5  4.5  5.5  6.5  7.5  8.5  9.5 10.5
> 
>>round(x)
> 
>  [1]  0  2  2  4  4  6  6  8  8 10 10
> 
>>cbind(x,round(x))
> 
>          x   
>  [1,]  0.5  0
>  [2,]  1.5  2
>  [3,]  2.5  2
>  [4,]  3.5  4
>  [5,]  4.5  4
>  [6,]  5.5  6
>  [7,]  6.5  6
>  [8,]  7.5  8
>  [9,]  8.5  8
> [10,]  9.5 10
> [11,] 10.5 10
> 
>  
>   Is this a well-known bug?
>  
> Thanks in advance,
>  
>  
> Dongseok Choi, Ph.D.
> Assistant Professor
> Division of Biostatistics
> Department of Public Health & Preventive Medicine
> Oregon Health & Science University
> 3181 SW Sam Jackson Park Road, CB-669
> Portland, OR 97239-3098
> TEL) 503-494-5336
> FAX) 503-494-4981
> choid at ohsu.edu
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html

On Tue, 22 Feb 2005 10:10:58 -0800, "Dongseok Choi" <choid at
ohsu.edu>
wrote :
>Hello,
> 
>  I found that round() does not behave as I expected.
>  Have you had similar experience as following?
> 
>> x<-seq(0.5,10.5,by=1)
>> x
> [1]  0.5  1.5  2.5  3.5  4.5  5.5  6.5  7.5  8.5  9.5 10.5
>> round(x)
> [1]  0  2  2  4  4  6  6  8  8 10 10
>> cbind(x,round(x))
>         x   
> [1,]  0.5  0
> [2,]  1.5  2
> [3,]  2.5  2
> [4,]  3.5  4
> [5,]  4.5  4
> [6,]  5.5  6
> [7,]  6.5  6
> [8,]  7.5  8
> [9,]  8.5  8
>[10,]  9.5 10
>[11,] 10.5 10
>
> 
>  Is this a well-known bug?
As others have said, it's not a bug at all.  If you would like to
round up instead, what you should do is use a function like this:
> roundup <- function(x) trunc(x+0.5)
> x <- -5:5 + 0.5
> x
 [1] -4.5 -3.5 -2.5 -1.5 -0.5  0.5  1.5  2.5  3.5  4.5 
5.5
> round(x)
 [1] -4 -4 -2 -2  0  0  2  2  4  4  6
> roundup(x)
 [1] -4 -3 -2 -1  0  1  2  3  4  5  6


If this doesn't handle negatives the way you want, play around a bit
with abs().

Duncan Murdoch