By a random chance, when I use options(digits = X), where X represents a number. My questions is when I set this X to different numbers, I could observe an interesting phenomenon in R.
When I print a numeric number, everything looks fine:
> print(1.8)
[1] 1.8
But when I set digits = 18, the number looks weird and round does not have an effect on this:
> options(digits = 18)
> 1.8
[1] 1.80000000000000004
> round(1.8, 1)
[1] 1.80000000000000004
The number looks fine when I set digits = 17:
> options(digits = 17)
> 1.8
[1] 1.8
I tested this and found that the number looks fine when digits < 18, but will have these weird looking once the digits is set to be at least 18.
Moreover, if I test if two numebers are equal using logical expressions, I have this:
> 1.80000000000000004 == 1.79999999999999999
[1] TRUE
It seesm that R internally does roundings on 1.80000000000000004 and 1.79999999999999999. My problem is: if I truly want to compare these two exact numbers (1.80000000000000004 and 1.79999999999999999), R would still think that they are the same.
Any insights on this will be appreciated. I am using R 4.1-0.
