[Rd] is class2 Parameter's Documentation is Ambiguous

[Thierry Onkelinx]

Dear Dario,

You misunderstood the documentation of is(). class1 refers to extends().
is() only uses class2, not class1.

I'd use inherits(your_object, "DataFrame") and inherits(your_object,
"data.frame"). The latter is probably redundant.

Best regards,

ir. Thierry Onkelinx
Statisticus / Statistician

Vlaamse Overheid / Government of Flanders
INSTITUUT VOOR NATUUR- EN BOSONDERZOEK / RESEARCH INSTITUTE FOR NATURE AND
FOREST
Team Biometrie & Kwaliteitszorg / Team Biometrics & Quality Assurance
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Op di 16 aug. 2022 om 12:01 schreef Dario Strbenac via R-devel <
r-devel using r-project.org>:

> Good day,
>
> It appears that class2 needs to be of length 1.
>
> > is(4, c("data.frame", "DataFrame"))
> Error in is(4, c("data.frame", "DataFrame")) :
>   length(class2) == 1L is not TRUE
>
> However, the documentation is "class1, class2: character strings giving
> the names of each of the two classes between which is relations are to be
> examined"
>
> Also, class1 is not a parameter of the is function. It is a parameter of
> the extends function. I think the mention of "is relations" is unintended.
> Can the documenation be rewritten to remove the ambiguity for these?
>
> --------------------------------------
> Dario Strbenac
> University of Sydney
> Camperdown NSW 2050
> Australia
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