[Rd] levels for list and data.frame

[Gregor Gorjanc]

Martin Maechler wrote:
>>>>>>"Gregor" == Gregor Gorjanc <gregor.gorjanc at gmail.com>
>>>>>>    on Tue, 21 Mar 2006 20:50:21 +0100 writes:
> 
> 
>     Gregor> Martin Maechler wrote:
>     >> Hi Gregor,
>     >> 
>     >> before even considering methods for "list" and
>     >> "data.frame", can you explain why you think it is
>     >> important for levels() to become a generic function at
>     >> all?  For me, levels belong to factors (or then to
>     >> contour plots, or co-plots ) but exactly because level is
>     >> a too generic word, it seems to me to be problematic as a
>     >> generic function.
>     >> 
>     >> How would describe the purpose of the levels() generic?
>     >> 
> 
>     Gregor> You are right. I was in situation where I wanted to
>     Gregor> get levels from all entries (factors) of a list and
>     Gregor> considered to write a method for this instead of
>     Gregor> always using lapply(). It went quite smoothly, if I
>     Gregor> skip R CMD check error. After that I began to think
>     Gregor> and post a question to R-devel. Perhaps levels is
>     Gregor> really to generic, however one can set levels also
>     Gregor> for non-factors. Although, I agree that this is of
>     Gregor> no use. I was also playing with levels<- and find it
>     Gregor> quite hard to do something general and usable for
>     Gregor> lists and data.frame.
> 
>     Gregor> If we put levels aside, is there any opinion/policy
>     Gregor> about list, data.frame methods? Just curiosity.
> 
> I don't understand the question.  Do you mean the question if
> methods should be written for "list" or for "data.frame" (which
> inherit from "list")?

Yes.

> But in any case, can you please take this back to R-devel?
> It has started there, and people should be able to see the
> continuation / conclusion.
> 

Hmm, replay all to your mail does not include r-devel, weird. Done.

-- 
Lep pozdrav / With regards,
    Gregor Gorjanc

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