[R] [External] R rounding problem?

[Richard M. Heiberger]

FAQ 7.31

On Fri, Sep 4, 2020 at 12:47 AM array chip via R-help
<r-help using r-project.org> 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?
>
> Thanks,
>
> Yi
>
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