[R] Creating NA equivalent

Chris Evans chr|@ho|d @end|ng |rom p@yctc@org
Tue Dec 21 12:16:55 CET 2021

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!


----- Original Message -----
> From: "Duncan Murdoch" <murdoch.duncan using gmail.com>
> To: "Marc Girondot" <marc_grt using yahoo.fr>, r-help using 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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> and provide commented, minimal, self-contained, reproducible code.

Chris Evans (he/him) <chris using 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/

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