[R] R rounding problem?

[JRG]

On 2020-09-04 00:46, array chip via R-help wrote:
> Hello,
>
> I made a mistake today on simple counting in R, that almost got me into trouble. After trying multiple times, I finally figured out it's rounding issue in R.
>
> For exmaple, when I just simply type:
>
>> (6.9-6.3) > 0.6
> [1] TRUE
>
> 6.9-6.3 should be 0.6 exactly, but R thinks that it's greater than 0.6!!
>
> Similarly, R thinks 5.6-5.5 is smaller than 0.1:
>
>> (5.6-5.5) < 0.1
> [1] TRUE
>
> Why is the above happening? This rounding issue seems to be small, but this could cause serious problem in real world.
>
> Can anyone shed a light on how to avoid the issue?


Maybe learn a little bit about digital arithmetic?



---JRG




> Thanks,
>
> Yi
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.