[R] Is it possible to define another kind of NA

[Dustin Tran]

Hi Marc,

This may be a helpful link: http://stackoverflow.com/questions/16074384/specify-different-types-of-missing-values-nas
> On Nov 9, 2014, at 1:07 PM, Marc Girondot <marc_grt at yahoo.fr> wrote:
> 
> Dear member list,
> 
> In many experimental sciences, there is a lower detection limit (LDL) when a dosage of a product is done. Then some samples are evaluated to be below this limit.
> I search for the best way to indicate in a data.frame that some values are such LDL. Ideally, an equivalent of NA would be the best.
> Until now I manage by indicating all the column in characters.
> So the question is: is it possible to define a value that could be named LDL and that could take place in vectors or data.frame such as:
> v <- c(0.2, 0.28, LDL, 0.9) is the same way that NA can be used.
> with of course a function is.ldl(v) that would return F F T F
> 
> Thanks a lot for any direction to solve this
> 
> Marc
> 
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