R devel - May 2021 - 1954 from NA

Hi Adrian,

I had the same thought as Luke. It is possible that you can develop an
ALTREP that carries around the tagging information you're looking for in a
way that is more persistent (in some cases) than R-level attributes and
more hidden than additional user-visible columns.

The downsides to this, of course, is that you'll in some sense be doing the
same "extra vector for each vector you want tagged NA-s within" under
the
hood, and that only custom machinery you write will recognize things as
something other than bog-standard NAs/NaNs.  You'll also have some problems
with the fact that data in ALTREPs isn't currently modifiable without
losing ALTREPness. That said, ALTREPs are allowed to carry around arbitrary
persistent information with them, so from that perspective making an ALTREP
that carries around a "meaning of my NAs" vector of tags in its
metadata
would be pretty straightforward.

Best,
~G

On Mon, May 24, 2021 at 7:30 AM Adrian Du?a <dusa.adrian at gmail.com>
wrote:
> Hi Taras,
>
> On Mon, May 24, 2021 at 4:20 PM Taras Zakharko <taras.zakharko at
uzh.ch>
> wrote:
>
> > Hi Adrian,
> >
> > Have a look at vctrs package ? they have low-level primitives that
might
> > simplify your life a bit. I think you can get quite far by creating a
> > custom type that stores NAs in an attribute and utilizes vctrs proxy
> > functionality to preserve these attributes across different
operations.
> > Going that route will likely to give you a much more flexible and
robust
> > solution.
> >
>
> Yes I am well aware of the primitives from package vctrs, since package
> haven itself uses the vctrs_vctr class.
> They're doing a very interesting work, albeit not a solution for this
> particular problem.
>
> A.
>
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On Mon, May 24, 2021 at 5:47 PM Gabriel Becker <gabembecker at gmail.com>
wrote:
> Hi Adrian,
>
> I had the same thought as Luke. It is possible that you can develop an
> ALTREP that carries around the tagging information you're looking for
in a
> way that is more persistent (in some cases) than R-level attributes and
> more hidden than additional user-visible columns.
>
> The downsides to this, of course, is that you'll in some sense be doing
> the same "extra vector for each vector you want tagged NA-s
within" under
> the hood, and that only custom machinery you write will recognize things as
> something other than bog-standard NAs/NaNs.  You'll also have some
problems
> with the fact that data in ALTREPs isn't currently modifiable without
> losing ALTREPness. That said, ALTREPs are allowed to carry around arbitrary
> persistent information with them, so from that perspective making an ALTREP
> that carries around a "meaning of my NAs" vector of tags in its
metadata
> would be pretty straightforward.
>
Oh... now that is extremely interesting.
It is the first time I came across the ALTREP concept, so I need to study
the way it works before saying anything, but definitely something to
consider.

Thanks so much for the pointer,
Adrian

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