[Rd] [R] unvectorized option for outer()

Duncan Murdoch murdoch at stats.uwo.ca
Tue Nov 1 16:56:54 CET 2005

On 11/1/2005 10:16 AM, Thomas Lumley wrote:
> On Tue, 1 Nov 2005, Duncan Murdoch wrote:
>> The version I posted yesterday did indeed mess up when some arguments were 
>> unspecified.  Here's a revision that seems to work in all the tests I can 
>> think of.  I also added the SIMPLIFY and USE.NAMES args from mapply to it, 
>> and a sanity check to the args.
>> I did notice and work around one buglet in mapply:  if you choose not to 
>> vectorize any arguments, you don't get a call to the original function, 
>> mapply returns "list()".
>> For example,
>>> mapply(function(x) x^2, MoreArgs = list(x=2))
>> list()
>> whereas I would think 4 is a more logical answer.
> I don't agree at all.  The answer should be the length of the longest 
> vectorised argument, and it is.

I do agree that if I'd specified something like

mapply(function(x) x^2, x=numeric(0))

then the answer (which is again list()) would be correct.  But
what is the length of the longest item in an empty set?  I'd say it's 

Duncan Murdoch

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