[R-pkg-devel] tibbles are not data frames

[Göran Broström]

Hej Stefan,

On 2017-09-26 10:57, Stefan McKinnon Høj-Edwards wrote:
> Hi Göran,
> 
> Could you please elaborate on which kind of subsetting that Hadley dislikes?
> I am yet to encounter operations on data frames that are not possible on 
> tribbles.

For instance, if 'dat' is a data frame, dat[1:3, 5] returns a vector of 
length 3. If 'dat' is a tibble, you do dat[[5]][1:3] to get the same 
vector. A tibble never 'drops dimensions'. See Hadley's book, on the web.

Göran

> 
> Kindly,
> Stefan McKinnon Hoj-Edwards
> 
> Stefan McKinnon Høj-Edwards
> ph.d. Genetics
> +44 (0)776 231 2464
> +45 2888 6598
> Skype: stefan_edwards
> 
> 2017-09-26 8:30 GMT+01:00 Göran Broström <goran.brostrom at umu.se 
> <mailto:goran.brostrom at umu.se>>:
> 
>     I am beginning to get complaints from users of my CRAN packages
>     (especially 'eha') to the effect that they get error messages like
>     "Error: Unsupported use of matrix or array for column indexing".
> 
>     It turns out that they are sticking in tibbles into functions that
>     expect data frames as input. And I am using the kind of subsetting
>     that Hadley dislikes (eha is an old package, much older than
>     tibbles). It is of course a simple matter to change the code so it
>     handles both data frames and tibbles correctly, but this affects
>     many functions, and it will take some time. And when the next guy
>     introduces 'troubles' as an improvement of 'tibbles', I will have to
>     rewrite the code again.
> 
>     While I like Hadley's way of doing it, I think it is a mistake to
>     let a tibble also be of class data frame. To me it is a matter of
>     inheritance and backwards compability: A tibble should add nice
>     things to a data frame, not change basic behaviour, in order to call
>     itself a data frame.
> 
>     Is it correct to let a tibble be of class "data.frame"?
> 
>     Göran Broström
> 
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