[R] all(logical(0)) and any(logical(0))
bates at stat.wisc.edu
Thu Apr 15 17:34:35 CEST 2004
"Liaw, Andy" <andy_liaw at merck.com> writes:
> I wrote:
> > I was bitten by the behavior of all() when given logical(0):
> > It is TRUE!
> > (And any(logical(0)) is FALSE.) Wouldn't it be better to
> > return logical(0)
> > in both cases?
> I guess the behavior is consistent with:
> > prod(numeric(0))
>  1
> > sum(numeric(0))
>  0
> but why?
The operation applied to a zero-length vector returns the identity
element of the operator. The identity element of * is 1, of + is 0,
of & is TRUE and of | is FALSE.
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