correction to the previously asked question (about merging factors)

In a message dated 2/5/2004 12:25:01 PM Pacific Standard Time, 
svetlana.eden at vanderbilt.edu writes:
I have two factors l1, l2, and I'd like to merge them.

(Remark:       The factors can not be converted to charaters)

Function c() does not give me the result I want:

l1 = factor(c('aaaa', 'bbbb'))
l2 = factor(c('ccc', 'dd'))
lMerge = factor(c(l1, l2))
lMerge

[1] 1 2 1 2
Levels: 1 2

I'd like to merge l1 and l2 and to get lMerge 
----------------------------------------------

[1] aaaa bbbb ccc dd
Levels: aaaa bbbb ccc dd