Re: NA assignment for character vector

[Spencer Graves <spencer.graves@PDF.COM>]

That's one of the difference between S-Plus and R.  In R 1.6.2, I just 
got the following:
> vec <- letters[1:5]
> vec[4] <- NA
> is.na(vec)
[1] FALSE FALSE FALSE  TRUE FALSE
> vec == "NA"
[1] FALSE FALSE FALSE    NA FALSE

People wishing to write code that works in both S-Plus and R need to be 
aware of this.
Spencer Graves

Sundar Dorai-Raj wrote:
> Stephen Lake wrote:
>
> > Hi S-users,
> >
> > Could someone please tell me how I can assign NA's to
> > character vectors and matrices? The usual element
> > assignment does not seem to work. Here is an example:
> >
> >
> > > vec <- letters[1:5]
> > > vec
> >
> > [1] "a" "b" "c" "d" "e"
> >
> > > vec[4] <- NA
> > > vec
> >
> > [1] "a" "b" "c" "NA" "e"
> >
> > > is.na(vec)
> >
> > [1] F F F F F
> >
> > If instead of letters[1:5] I assign the numeric vector
> > 1:5, the behavior is as expected, ie the is.na() function
> > detects a NA at position 4 of the vector.
> >
> > Any help would be greatly appreciated,
> > Steve Lake
> >
> > PS I am using Version 6.0 Release 1 for Sun SPARC, SunOS 5.5
>  From ?is.na:
>
> REQUIRED ARGUMENTS:
> x     an S-PLUS object, which should be logical, numeric, or complex.
>
> WARNING:
> This is always FALSE when x is of mode "character".
>
>
> You should use == "NA" if x is character. As in:
>
>  > vec <- letters[1:5]
>  > vec[4] <- NA
>  > vec == "NA"
> [1] F F F T F
>
>
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