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

On Tue, Sep 26, 2017 at 11:56 AM, G?bor Cs?rdi <csardi.gabor at gmail.com>
wrote:

I have yet to see an OOP system in which a subclass cannot override the
methods
of its superclass. Not only is this in line with OOP paradigms, it is
actually one of
the essential OOP features.

Fair enough. And I shouldn't have used the word "inherit" in the first
place, we're talking S3 after all. Fwiw, overriding a method to do the
exact same except for one detail isn't encouraged in the OOP world either.

To be more constructive, if you have a function that only works with
data frame inputs, then
it is good practice to check that the supplied input is indeed a data
frame. This is
independent of tibbles.

Actually it's not independent of tibbles as illustrated by others.
is.data.frame() returns TRUE for tibbles. It doesn't for matrices or
vectors.

In practice it seems to me that an easy fix is to just call
as.data.frame on the input. This should
either convert it to a data frame, or throw an error. For tibbles it
drops the tbl* classes.

This would also allow matrices or vectors to be converted to data.frames,
and that might or might not be warranted.

I agree that the S3 system allows you to do this, and think it's up to the
package manager to decide whether or not they would allow their users to
use tibbles instead of data.frame objects.

I think the bigger frustration is that tibble users are more prone to
expect all code to work exactly like it does with data.frames. Which it
obviously doesn't.

Joris Meys
Statistical consultant

Ghent University
Faculty of Bioscience Engineering
Department of Mathematical Modelling, Statistics and Bio-Informatics

tel : +32 9 264 59 87
Joris.Meys at Ugent.be
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