I have two different data frame, in one of them I have the information id , in the other I have the id and a vector n, I would like associate the values of n to id in the first dataframe. 
for exemple:
 df1 <-data.frame(
  id = c(1,1,1,2,2,3,3,3,3)
  )
df2 <- data.frame(
  id = c(1,2,3),
   n = c(5,9,8)
  )
I would like as output:
df1:
id   n
1    5
1    5
1    5
2    9
2    9
3    8
3    8
3    8
3    8
 
     
    