[R] Rounding problem R vs Excel

[Duncan Murdoch]

On Mon, 2 Jun 2003 20:50:20 -0400, you wrote:

>Does this script do what you want?
>
>cround <- function(x,digits=0) {
>   a <- ifelse(x>0,.5,-.5)
>   if (digits==0) {
>     floor(x+a)
>   } else {
>     m <- 10^digits
>     floor(x*m+a)/m
>   }
>}

No, the problem is that R uses binary formats, and some numbers aren't
representable there.  So for example,

> cround(0.145,2)
[1] 0.14

because 0.145 isn't representable exactly, and is actually being
represented as 0.14999999999 or something similar.

Duncan Murdoch