[R] Factor function

[Ista Zahn]

Hi Lisa,

NA != "NA"

The first represents a missing observation, the second represents a
character string.

HTH,
Ista


On Mon, Apr 25, 2011 at 3:53 PM, Lisa <lisajca at gmail.com> wrote:
> Dear All,
>
> I just want to remove “NA” from the levels of a factor.  For example:
>
> d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"),
> ncol=3, byrow=TRUE))
>
>> factor(d[, 3], exclude=NA)
> [1] xx yy NA
> Levels: NA xx yy
>
> But “NA” is still listed in the levels. How can I solve this problem? Thanks
> in advance.
>
> Lisa
>
>
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-- 
Ista Zahn
Graduate student
University of Rochester
Department of Clinical and Social Psychology
http://yourpsyche.org