R help - Dec 2021 - Creating NA equivalent

I am neither a programmer nor a professional statistician but this topic
interests me because:

1) I remember from long, long ago that S had a way to create labels that could
denote multiple ways
   in which a value could be missing that was sometimes useful to me as my field
sometimes has
   such situations.  In R I handle this with a second variable but I can see
that using attributes
   is cleaner and might have real benefits when doing missing value analyses. 
That might raise
   questions about whether some of the nice packages that help with missing
value analyses would
   take on board some standardised use of attributes for this.

2) I think Marc's question LDL/UDL is about a very particular sort of value
that isn't missing
   and _is_ censored but not in survival analysis meaning of censored. (At
least, it's not the same
   to my mind, perhaps it is?  To me the difference is that I most often hit the
LDL/UDL issue
   in data that don't have much, or any, time frame.) Again, this comes up a
lot for me where
   people are given limited possible answers in questionnaires and I've
often wondered if I
   should explore simulating probability models for an the "off the
edge" value on a latent
   variable beneath/behind the measured responses.  I'd be very grateful to
hear of any work
   in R packages (to stay only just "off the edge" of the posting   
guide).  Or of any work a
   long the lines that Duncan offers, that sort of pulls this toward    base R,
though that sounds
   to me as if it would be a huge undertaking.

I'm very interested to hear any thoughts on either aspect.

Seasonal (mutivalued) greetings to all!

Chris

----- Original Message -----
> From: "Duncan Murdoch" <murdoch.duncan at gmail.com>
> To: "Marc Girondot" <marc_grt at yahoo.fr>, r-help at
r-project.org
> Sent: Tuesday, 21 December, 2021 10:26:12
> Subject: Re: [R] Creating NA equivalent
> On 20/12/2021 11:41 p.m., Marc Girondot via R-help wrote:
>> Dear members,
>> 
>> I work about dosage and some values are bellow the detection limit. I
>> would like create new "numbers" like LDL (to represent lower
than
>> detection limit) and UDL (upper the detection limit) that behave like
>> NA, with the possibility to test them using for example is.LDL() or
>> is.UDL().
>> 
>> Note that NA is not the same than LDL or UDL: NA represent missing
data.
>> Here the data is available as LDL or UDL.
>> 
>> NA is built in R language very deep... any option to create new version
>> of NA-equivalent ?
>> 
> 
> There was a discussion of this back in May.  Here's a link to one
> approach that I suggested:
> 
>   https://stat.ethz.ch/pipermail/r-devel/2021-May/080776.html
> 
> Read the followup messages, I made at least one suggested improvement.
> I don't know if anyone has packaged this, but there's a later
version of
> the code here:
> 
>   https://stackoverflow.com/a/69179441/2554330
> 
> Duncan Murdoch
> 
> ______________________________________________
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> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
-- 
Chris Evans (he/him) <chris at psyctc.org> 
Visiting Professor, UDLA, Quito, Ecuador & Honorary Professor, University of
Roehampton, London, UK.
Work web site: https://www.psyctc.org/psyctc/ 
CORE site:     https://www.coresystemtrust.org.uk/
Personal site: https://www.psyctc.org/pelerinage2016/
OMbook:        https://ombook.psyctc.org/book/

Hi Chris,

The survival package provides machinery for handling censored observations.
Whether time is censored or some other type of variable (e.g., viral load due to
some lower detection limit) does not make a fundamental difference. In fact, the
type of model you are thinking of with 2) is a Tobit model, which can be fitted
using the survival package (or censReg).

Best,
Wolfgang
>-----Original Message-----
>From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of Chris
Evans
>Sent: Tuesday, 21 December, 2021 12:17
>To: Duncan Murdoch
>Cc: r-help at r-project.org
>Subject: Re: [R] Creating NA equivalent
>
> I am neither a programmer nor a professional statistician but this topic
interests me because:
> 
> 1) I remember from long, long ago that S had a way to create labels that
could
>    denote multiple ways in which a value could be missing that was
sometimes
>    useful to me as my field sometimes has such situations.  In R I handle
this
>    with a second variable but I can see that using attributes is cleaner
and
>    might have real benefits when doing missing value analyses.  That might
>    raise questions about whether some of the nice packages that help with
>    missing value analyses would take on board some standardised use of
>    attributes for this.
> 
> 2) I think Marc's question LDL/UDL is about a very particular sort of
value
>    that isn't missing and _is_ censored but not in survival analysis
meaning
>    of censored. (At least, it's not the same to my mind, perhaps it is?
To me
>    the difference is that I most often hit the LDL/UDL issue in data that
>    don't have much, or any, time frame.) Again, this comes up a lot for
me
>    where people are given limited possible answers in questionnaires and
I've
>    often wondered if I should explore simulating probability models for an
the
>    "off the edge" value on a latent variable beneath/behind the
measured
>    responses.  I'd be very grateful to hear of any work in R packages
(to stay
>    only just "off the edge" of the posting    guide).  Or of any
work a long
>    the lines that Duncan offers, that sort of pulls this toward    base R,
>    though that sounds to me as if it would be a huge undertaking.
> 
> I'm very interested to hear any thoughts on either aspect.
> 
> Seasonal (mutivalued) greetings to all!
> 
> Chris