[Rd] Floating point issue

[Dirk Eddelbuettel]

On 10 July 2022 at 16:00, Antoine Fabri wrote:
| Dear r-devel,
| 
| For some numbers, the printed value is not equivalent to the input :
| 
| options(scipen = 999)
| ## GOOD
| 1e24
| #> [1]  999999999999999983222784
| 1e24 == 999999999999999983222784
| #> [1] TRUE
| 
| ## BAD
| 1e25
| #> [1] 10000000000000000905969664
| 1e25 == 10000000000000000905969664
| #> [1] FALSE
| 
| ## STILL BAD
| 10000000000000000905969664
| #> [1] 10000000000000003053453312
| 
| ## GOOD AGAIN
| 10000000000000003053453312
| #> [1] 10000000000000003053453312
| 
| # Additionally
| 10000000000000000000000000 == 1e25
| #> [1] FALSE
| 
| Are these bugs ?

No, that is how computers work (with floating point numbers).

Please R FAQ 7.31 "Why doesn’t R think these numbers are equal?" at
  https://cran.r-project.org/doc/FAQ/R-FAQ.html#Why-doesn_0027t-R-think-these-numbers-are-equal_003f
and the references therein for more.

Dirk

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