[R] calculate differences - strange outcome

[Duncan Murdoch]

Kunzler, Andreas wrote:
> Dear List,
>
> I ran into some trouble by calculating differences. For me it is
> important that differences are either 0 or not.
>
> So I don't understand the outcome of this calculation
>
> 865.56-(782.86+0+63.85+18.85+0)
> [1] -1.136868e-13
>
> I run R version 2.71 on WinXP
>
> I could solve my problem by using
> round()
> but I would like to know the reason.
> Maybe someone can help me?

This is FAQ 7.31.

Duncan Murdoch