# [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

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
>
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> guide.html
> and provide commented, minimal, self-contained, reproducible code.

--
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

```