Duplication of elements from a data frame

Question

I have a data frame that looks like this:

x <- as.data.frame(matrix(data = c("a", "b", "c", 1, 2, 3), 
                      ncol = 2,
                      nrow = 3,
                      byrow = FALSE))

> x
  V1 V2
1 a  1
2 b  2
3 c  3

Lets say I want to duplicate element x[1,2] four times, element x[2,2] six times and element x[3,2] five times and save them all in a new data frame.

> v
  V1
  1
  1
  1
  1
  2
  2
  ...

I know I could do it by using rep, but i'm wondering if there is a more comfortable way.

Answer 1

Here's another alternative

data.frame(v=rep(as.numeric(x[,2]), c(4,6,5)))

If you want to keep the factors, then omit as.numeric(·)

data.frame(v=rep(x[,2], c(4,6,5)))

Answer 2

you could use something like

TheseRows <- c(1, 2, 3)
NManyReps <- c(4, 6, 5)
x[, 2][ do.call(rep, list(TheseRows, NManyReps)) ]