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

Lee, Chel Hee chl948 at mail.usask.ca
Sun Nov 9 19:30:11 CET 2014

 > LDL <- NA_real_
 > is.LDL <- is.na
 > v <- c(0.2, 0.28, LDL, 0.9)
 > v
[1] 0.20 0.28   NA 0.90
 > is.LDL(v)

Hope this helps.

Chel Hee Lee

On 11/9/2014 12:07 PM, Marc Girondot 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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