How to concatenate factors, without them being converted to integer level?

Question

I was surprised to see that R will coerce factors into a number when concatenating vectors. This happens even when the levels are the same. For example:

>         


        

Answer 1

Wow, I never realized it did that. Here is a work-around:

x <- c(facs[1 : 3], facs[4 : 5]) 
x <- factor(x, levels=1:nlevels(facs), labels=levels(facs))
x

With the output:

[1] i    want to   be   a   
Levels: a an be factor i integer not to want

It will only work if the two vectors have the same levels as here.