[R] Why can't R understand if(num!=NA)?
marc_schwartz at me.com
Fri May 3 18:02:48 CEST 2013
On May 3, 2013, at 10:24 AM, jpm miao <miaojpm at gmail.com> wrote:
> I have a program, when I write
> it yields an error message.
> However, if I write
> it works.
> Why doesn't the first statement work?
NA is undefined:
> NA == NA
> NA != NA
Therefore the equality you are attempting does not return a TRUE or FALSE result, it is unknown and NA is returned. ?is.na was designed specifically to test for the presence of an NA value and return a TRUE or FALSE result which can then be tested.
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