Re: [Rd] slot named C

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Mon 17 Apr 2006 - 15:09:42 GMT

On Mon, 17 Apr 2006, Paul Gilbert wrote:

>
>
> Prof Brian Ripley wrote:
>> On Mon, 17 Apr 2006, Paul Gilbert wrote:
>>
>>> Ok, but I'm surprised. I thought partial matching only happened for
>>> named arguments. I guess I've been lucky.
>>
>> Here C is named, so what did you mean?
>
> Now I guess I've really been confused. I thought named arguments in a
> function were the optional ones you named when you define the function
> (with name=default, so Class is not a named argument in the call to

All formal arguments _are_ named. Some have defaults. So the allowed forms are

name
name=default

> new). Are you saying the named arguments are the ones you name when you
> call the function?

That's the standard usage. See the Blue Book pp.37-8 (and I reckon that the posting guide asked you to look that up for yourself: so please re-read it).

>
> Paul
>>
>> Partial matching happens for all arguments called by name, except for
>> those following ... in the formals.
>>
>>>
>>> Paul
>>>
>>> Prof Brian Ripley wrote:
>>>> It's an error in your usage The args of new() are
>>>>
>>>>> args(new)
>>>> function (Class, ...)
>>>>
>>>> and what does 'C' match? You need to name your arguments here.
>>>>
>>>> On Mon, 17 Apr 2006, Paul Gilbert wrote:
>>>>
>>>>> "C" appears to be an illegal name for a slot in an S4 class (example
>>>>> below).
>>>>
>>>> It is rather an example of something which does not work.
>>>>
>>>> foo <- new("testobj")
>>>> foo@C <- 2
>>>>
>>>> does, for example.
>>>>
>>>>> If this is a known limitation, and not a bug, it would be nice
>>>>> if it were caught by setClass.
>>>>>
>>>>> Paul Gilbert
>>>>>
>>>>>> setClass("testobj", representation ( C = "numeric"))
>>>>> [1] "testobj"
>>>>>> new("testobj", C= 2)
>>>>> Error in methodsPackageMetaName("C", name) :
>>>>> 'The name of the object (e.g,. a class or generic function) to
>>>>> find in the meta-data' must be a single string (got an object of class
>>>>> "numeric")
>>>>>
>>>>>> setClass("testobj", representation ( C. = "numeric"))
>>>>> [1] "testobj"
>>>>>> new("testobj", C.= 2)
>>>>> An object of class "testobj"
>>>>> Slot "C.":
>>>>> [1] 2
>>>>> ====================================================================================
>>>>>
>>>>>
>>>>>
>>>>> La version franšaise suit le texte anglais.
>>>>>
>>>>> ------------------------------------------------------------------------------------
>>>>>
>>>>>
>>>>>
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>>>>>
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>>>>>
>>>>>
>>>>
>>> ====================================================================================
>>>
>>>
>>> La version franšaise suit le texte anglais.
>>>
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>>
> ====================================================================================
>
> La version franšaise suit le texte anglais.
>
> ------------------------------------------------------------------------------------
>
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>
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-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595


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Received on Tue Apr 18 01:17:42 2006

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