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

On Tue, Sep 26, 2017 at 2:30 AM, G?ran Brostr?m <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.

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