[R] write a loop for tallies

[john polo]

Dear R users,

I have a list of numbers such as

 > n
 [1] 3000 4000 5000 3000 5000 6000 4000 5000 7000 5000 6000 7000

and i'd like to set up a loop that will keep track of the number of 
occurences of each of the values that occur in the list, e.g.

3000: 2
4000: 2
5000: 4

I came up with the following:

a<- for (i in 1:length(n)) {
 r<-0
 s<-0
 t<-0
 u<-0
 v<-0
 ifelse(n[i] == "3000", r <- r+1,
 ifelse(n[i] == "4000", s <- r+1,
ifelse(n[i] == "5000", t <- r+1,
ifelse(n[i] == "6000", u <- r+1,
ifelse(n[i] == "7000", v <- r+1, NA)))))
r<-sum(r)
s<-sum(s)
t<-sum(t)
u<-sum(u)
v<-sum(v)
cat("r = ", r, "\n")
cat("s = ", s, "\n")
cat("t = ", t, "\n")
cat("u = ", u, "\n")
cat("v = ", v, "\n")
}

However, this is the output:

r =  1
s =  0
t =  0
u =  0
v =  0
r =  0
s =  1
t =  0
u =  0
v =  0
r =  0
s =  0
t =  1
u =  0
v =  0
r =  1
s =  0
t =  0
u =  0
v =  0
r =  0
s =  0
t =  1
u =  0
v =  0
r =  0
s =  0
t =  0
u =  1
v =  0
r =  0
s =  1
t =  0
u =  0
v =  0
r =  0
s =  0
t =  1
u =  0
v =  0
r =  0
s =  0
t =  0
u =  0
v =  1
r =  0
s =  0
t =  1
u =  0
v =  0
r =  0
s =  0
t =  0
u =  1
v =  0
r =  0
s =  0
t =  0
u =  0
v =  1

How should i write this loop, please? I've tried variations with "if" 
instead of "ifelse" and receive errors about "unexpected {" or 
"unexpected )".
 
regards,
john