[R] removing NA as a level

[Petr Pikal]

On 6 Dec 2004 at 13:58, Anne wrote:

> Dear R-helpers,
> I have a problem which I suppose is trivila, but...
> I have included NA values as factors ( (to be able to make nice
> printed summaries with NAs % ba category ) with the following code
> 
> dat$x.f<-factor(dat$x, exclude=NULL);
> levels(dat$x.f)<-c("A1","A2","A3","A4","NA"); length(dat$x.f)
> 
> Now, I want to impute the missing values. Is there a nice way to drop
> the NA factor instead of rewriting something of the sort 
>  dat$x.f<-factor(dat$x); levels(dat$x.f)<-c("A1","A2","A3","A4");
>  length(dat$x.f)?

Hi Anne
 
Is this 

dat$x.f[!is.na(dat$x.f), drop=T]

what you want?

?"[.factor"

Cheers
Petr


> 
> Thanks 
> 
> Anne
> 
> 
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> Anne Piotet
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> Email: anne.piotet at m-td.com
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Petr Pikal
petr.pikal at precheza.cz