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

Göran Broström goran.brostrom at umu.se
Tue Sep 26 16:27:04 CEST 2017

On 2017-09-26 15:37, Hadley Wickham wrote:
> On Tue, Sep 26, 2017 at 2:30 AM, Göran Broström <goran.brostrom at umu.se> wrote:
>> 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.
> Changing df[, x] to df[[x]] is not very hard and makes your code
> easier to understand because it more clearly conveys the intent that
> you want a single column.

Couldn't agree more: Not because it works with tibbles, but because it 
works with lists. And therefore with data frames. If we trust inheritance.


>> 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"?
> If it not inherit from data frame, it would be not work with the 99%
> of functions that work with data frames and don't deliberately take
> advantage of the dropping behaviour of [. In other words, it would be
> pointless.
> I decided to make [.tibble type-stable (i.e. always return a data
> frame) because this behaviour causes substantial problems in real data
> analysis code.
> I did it understanding that it would cause some package
> developers frustration, but I think it's better for a handful of
> package maintainers to be frustrated than hundreds of users creating
> dangerous code.

> Hadley

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