[Rd] Numerical error in R (win32) (PR#8909)

Peter Dalgaard
2006-05-29T16:49:09Z

teck.lim at imperial.ac.uk writes:

> Hi
>     I had observed the following problem in R (also C, Matlab, and Python).
> sprintf('%1.2g\n', 3.15)
> give 3.1 instead of 3.2 whereas an input of 3.75 gives 3.8.
> Java's System.out.printf is ok though.
>
> > round(3.75,1)
> [1] 3.8
> > round(3.15,1)
> [1] 3.1
>
> Similar outcome with sprintf in R.
>
>
> However, the right answer should be 3.2

According to what? Remember that we're dealing with finite precision
binary arithmetic here:

>  (3.15 - 3.1)<.05
[1] TRUE
>  abs(3.15 - 3.2)>.05
[1] TRUE

See also FAQ 7.31.

> Regards
> Teckpor
>

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