Re: NA's in string vector.

[Prof Brian D Ripley <ripley@stats.ox.ac.uk>]

On Thu, 6 Dec 2001, Vadim Kutsyy wrote:

> Is there a way to define NA's in string vector?
>
> > a<-c("a",NA,"b")
> > is.na(a)
> [1] F F F
> > a
> [1] "a"  "NA" "b"
> > a[2]<-NA
> > is.na(a)
> [1] F F F
>
> Splus converge all NA's to "NA", which make problem in data.frames.

Actually, that's a character vector, and for once the distinction matters.
Under S4, `string' is a separate class, and the way I know to do this is to
use the `string' class and is.na<-.  See the Green Book.

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
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