[R] all(logical(0)) and any(logical(0))

[Patrick Burns]

I suspect that some people still might not have caught why
the behavior is a good thing.

We want

any(c(A, B))

to give the same answer as

any(A) || any(B)

This should be the behavior even if all of the elements are
in one of the vectors.

This actually is useful in coding, though I can't think of any
specific instances at the moment.

Patrick Burns

Burns Statistics
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of S Poetry and "A Guide for the Unwilling S User")

Douglas Bates wrote:

>"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] 1
>>    
>>
>>>sum(numeric(0))
>>>      
>>>
>>[1] 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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