[R] multiple uses ifelse function

[message]

Readers,

Could someone please explain how to apply the function 'ifelse' to 
change a vector, for various conditions?

testseq<-seq(1:20)
testchange<-ifelse(testseq<=4,'x',testseq)
testchange<-c(ifelse(testseq<=4,'x',testseq),ifelse(testseq>=5,'y',testseq))

The last instruction causes the vector 'testchange' to change 
dimensions, when the result wanted is:

testchange
x x x x y y y y y y y y y y y y y y y y