[R] <NA> to NA

[Marc Schwartz]

On Mar 31, 2014, at 1:29 PM, eliza botto <eliza_botto at hotmail.com> wrote:

> Dear useRs,
> Sorry for such a ridiculous question but i really need to know that what is the difference between <NA> and NA and how to convert <NA> to NA.
> Thankyou very much in advance
> Eliza  		 	   


<NA> is the printed output that you would typically get when "NA" is an element in a factor:

> factor(NA)
[1] <NA>

> is.na(factor(NA))
[1] TRUE

> NA
[1] NA

> is.na(NA)
[1] TRUE


See ?factor for additional details.

It is, other than the displayed output, the same as a 'normal' NA, which is to say that the value is missing and otherwise undefined.

The behavior appears to evolve from the use of ?encodeString, which is called within print.factor:

> encodeString(NA)
[1] "<NA>"

> encodeString(NA, na.encode = FALSE)
[1] NA


The default for the 'na.encode' argument is TRUE, so you get the formatting of the NA as you observe for factors.

Regards,

Marc Schwartz