R help - Jul 2008 - factor question

Hi!

Suppose I have a factor:
> fac1 <-
factor(rep(c("dog","cat","tree"),c(2,3,4)))
> fac1
[1] dog  dog  cat  cat  cat  tree tree tree tree
Levels: cat dog tree
> length(fac1)
[1] 9

Now I want to get rid of the dogs:
> fac1 <- fac1[3:9]
> fac1
[1] cat  cat  cat  tree tree tree tree
Levels: cat dog tree
>
How should I remove the dog from the level, please?

Thanks in advance,
Edna Bell

Try:

fac1[3:9][drop=T]

On Thu, Jul 24, 2008 at 4:19 PM, Edna Bell <edna.bell01 at gmail.com>
wrote:
> Hi!
>
> Suppose I have a factor:
>
>> fac1 <-
factor(rep(c("dog","cat","tree"),c(2,3,4)))
>> fac1
> [1] dog  dog  cat  cat  cat  tree tree tree tree
> Levels: cat dog tree
>> length(fac1)
> [1] 9
>
> Now I want to get rid of the dogs:
>> fac1 <- fac1[3:9]
>> fac1
> [1] cat  cat  cat  tree tree tree tree
> Levels: cat dog tree
>>
> How should I remove the dog from the level, please?
>
> Thanks in advance,
> Edna Bell
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Henrique Dallazuanna
Curitiba-Paran?-Brasil
25? 25' 40" S 49? 16' 22" O

Hi Edna,

Because I am "always" subsetting, I keep the following function handy

mydata[] <- lapply(mydata, function(x) if(is.factor(x)) x[,drop=T] else x)

This will strip out all factor levels that have been dropped by a previous
subsetting operation. For novice users of R (though I am not suggesting that
you are) it's priceless.

The original author, as far as I know, is Andy Liaw (author of the
randomForest package).

HTH, Mark.


Edna Bell wrote:
> 
> Hi!
> 
> Suppose I have a factor:
> 
>> fac1 <-
factor(rep(c("dog","cat","tree"),c(2,3,4)))
>> fac1
> [1] dog  dog  cat  cat  cat  tree tree tree tree
> Levels: cat dog tree
>> length(fac1)
> [1] 9
> 
> Now I want to get rid of the dogs:
>> fac1 <- fac1[3:9]
>> fac1
> [1] cat  cat  cat  tree tree tree tree
> Levels: cat dog tree
>>
> How should I remove the dog from the level, please?
> 
> Thanks in advance,
> Edna Bell
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 
> 
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