[R] Catenating factors.

[Mike Lawrence]

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

ex.

#if your factor levels are letters
z=factor(unique(c(as.character(x),as.character(y))))

#if your factor levels are numbers
z=factor(unique(c(as.numeric(as.character(x)),as.numeric(as.character 
(y)))))


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
http://myweb.dal.ca/mc973993

"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