[Rd] na.omit inconsistent with is.na on list

[Iñaki Ucar]

On Thu, 12 Aug 2021 at 22:20, Gabriel Becker <gabembecker using gmail.com> wrote:
>
> Hi Toby,
>
> This definitely appears intentional, the first  expression of
> stats:::na.omit.default is
>
>    if (!is.atomic(object))
>
>         return(object)

I don't follow your point. This only means that the *default* method
is not intended for non-atomic cases, but it doesn't mean it shouldn't
exist a method for lists.

> So it is explicitly just returning the object in non-atomic cases, which
> includes lists. I was not involved in this decision (obviously) but my
> guess is that it is due to the fact that what constitutes an observation
> "being complete" in unclear in the list case. What should
>
> na.omit(list(5, NA, c(NA, 5)))
>
> return? Just the first element, or the first and the last? It seems, at
> least to me, unclear. A small change to the documentation to to add "atomic

> is.na(list(5, NA, c(NA, 5)))
[1] FALSE  TRUE FALSE

Following Toby's argument, it's clear to me: the first and the last.

Iñaki

> (in the sense of is.atomic returning \code{TRUE})" in front of "vectors"
> or similar  where what types of objects are supported seems justified,
> though, imho, as the current documentation is either ambiguous or
> technically incorrect, depending on what we take "vector" to mean.
>
> Best,
> ~G
>
> On Wed, Aug 11, 2021 at 10:16 PM Toby Hocking <tdhock5 using gmail.com> wrote:
>
> > Also, the na.omit method for data.frame with list column seems to be
> > inconsistent with is.na,
> >
> > > L <- list(NULL, NA, 0)
> > > str(f <- data.frame(I(L)))
> > 'data.frame': 3 obs. of  1 variable:
> >  $ L:List of 3
> >   ..$ : NULL
> >   ..$ : logi NA
> >   ..$ : num 0
> >   ..- attr(*, "class")= chr "AsIs"
> > > is.na(f)
> >          L
> > [1,] FALSE
> > [2,]  TRUE
> > [3,] FALSE
> > > na.omit(f)
> >    L
> > 1
> > 2 NA
> > 3  0
> >
> > On Wed, Aug 11, 2021 at 9:58 PM Toby Hocking <tdhock5 using gmail.com> wrote:
> >
> > > na.omit is documented as "na.omit returns the object with incomplete
> > cases
> > > removed." and "At present these will handle vectors," so I expected that
> > > when it is used on a list, it should return the same thing as if we
> > subset
> > > via is.na; however I observed the following,
> > >
> > > > L <- list(NULL, NA, 0)
> > > > str(L[!is.na(L)])
> > > List of 2
> > >  $ : NULL
> > >  $ : num 0
> > > > str(na.omit(L))
> > > List of 3
> > >  $ : NULL
> > >  $ : logi NA
> > >  $ : num 0
> > >
> > > Should na.omit be fixed so that it returns a result that is consistent
> > > with is.na? I assume that is.na is the canonical definition of what
> > > should be considered a missing value in R.
> > >
> >
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> >
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> >
>
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>
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-- 
Iñaki Úcar