[R] Catenating factors.

Mike Lawrence Mike.Lawrence at DAL.CA
Wed May 23 13:40:10 CEST 2007

It may be poor form, but whenever I deal with factors in this way I  
find as.character and as.numeric useful


#if your factor levels are letters

#if your factor levels are numbers

On 22-May-07, at 11:56 PM, Marc Schwartz wrote:

> On Wed, 2007-05-23 at 13:38 +1200, Rolf Turner wrote:
>> I was recently asked by one of new colleagues how to combine, or  
>> catentate,
>> or concatentate two factors.  If x and y are factors, doing c(x,y)  
>> appears
>> to coerce x and y to numeric mode before catenating them.  So what  
>> does one
>> do if one wants the result to be a factor whose levels are the  
>> union of the
>> levels of x and y?  I vaguely recall seeing this discussed in r- 
>> help, but I
>> can't find anything on it there, nor in the FAQ.
>> Am I missing something obvious?
> Rolf,
> I think that this thread from last November on R-devel may be helpful:
> http://tolstoy.newcastle.edu.au/R/e2/devel/06/11/1130.html
> HTH,
> Marc Schwartz
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Mike Lawrence
Graduate Student, Dalhousie University Department of Psychology

"The road to wisdom? Well, it's plain and simple to express:
Err and err and err again, but less and less and less."
- Piet Hein

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