[R] Factor function

[Petr PIKAL]

Hi


d<-data.frame(matrix(c("ww","ww","xx","yy","ww","yy","xx","yy","NA"), 
ncol=3, byrow=TRUE))

Change character value "NA" to missing value <NA>
d[d[,3]=="NA",3]<-NA

If you want drop any unused levels of a factor just use

factor(d[,3])
[1] xx   yy   <NA>
Levels: xx yy

Regards
Petr


r-help-bounces at r-project.org napsal dne 25.04.2011 23:03:15:

> Thank you for your reply again. I really know that NA is not "NA". I 
just
> want to figure out how to remove "NA" from the levels. Thanks again.
> 
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