[Rd] Deprecating partial matching in $.data.frame

peter dalgaard pdalgd at gmail.com
Fri Mar 22 09:31:57 CET 2013

On Mar 22, 2013, at 05:57 , Hervé Pagès wrote:

> Hi,
> Maybe a compromise would be to just issue a warning without
> deprecating? That way people who want to do anova(fit1)$P can
> still do it. When working interactively, it's certainly convenient
> (serious code however should probably stay away from partial matching).

That's what it does. Issuing a warning when users do X is pretty much equivalent to deprecating X.

> And so you keep the semantic consistent with lists because yes,
> consistency is important. data.frame inherits from list so any
> operation that works on a list is expected to work on a data.frame,
> preferably the same way (otherwise it will always be a BIG surprise
> to the user/programmer). For example if I have to maintain someone
> else code and see something like:
>    bar <- x$bar
> and I know that 'x' is a list that contains atomic vectors of the
> same length, I could have some good reasons to want to use a
> data.frame instead of a list. And I would assume it's safe to
> modify the code by adding the following line earlier in it:
>   x <- as.data.frame(x)
> But with the proposed change to $.data.frame, I cannot make this
> kind of assumption anymore...

No, but it's only a real problem if the component is not actually called "bar". You could make the same point for environments, but they never allowed partial matching:

> e <- as.environment(list(barbaric=666))
> e$bar
> e$barbaric
[1] 666

Peter Dalgaard, Professor
Center for Statistics, Copenhagen Business School
Solbjerg Plads 3, 2000 Frederiksberg, Denmark
Phone: (+45)38153501
Email: pd.mes at cbs.dk  Priv: PDalgd at gmail.com

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