Ouch! The values are **NOT** missing -- they are (left) censored, and need to be handled by appropriate censored data methods. I suggest you (all!) either read up on this or consult someone locally who has knowledge of such methods.
-- Bert Bert Gunter Genentech Nonclinical Biostatistics (650) 467-7374 "Data is not information. Information is not knowledge. And knowledge is certainly not wisdom." Clifford Stoll On Sun, Nov 9, 2014 at 10:40 AM, Dustin Tran <dustinviett...@gmail.com> wrote: > 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_...@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 >> >> ______________________________________________ >> R-help@r-project.org mailing list >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html >> and provide commented, minimal, self-contained, reproducible code. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.