[R] combining data from different datasets

[Gabor Grothendieck]

On Fri, Oct 24, 2008 at 11:37 AM, Dr Eberhard W Lisse <el at lisse.na> wrote:
>
> This looks very cool.
>
> But I must still make a plan with regards to country = "NA" (Namibia)
> or continent = "NA" (North America)
>
> But there are the vignettes.
>
> el
>

NA and "NA" are not the same:

> DF <- data.frame(x = c("a", "NA", NA))
> DF
     x
1    a
2   NA
3 <NA>
>
> is.na(NA)
[1] TRUE
> is.na("NA")
[1] FALSE