Multiplying vectors of different length in R

Question

I have a function:

v0 <- function(n) {
   seq(1:n)
}

and I need to create a function v1 which gives this result:

(1 2 3 -4 -5 -6 7 8 9 -10)            # if n <- 10   or
(1 2 3 -4 -5 -6 7 8 9 -10 -11 -12 13) # if n <- 13

But I keep getting a warning message when I do:

v1 <- function(n) {
    seq(1:n) * c(1,1,1,-1,-1,-1)
}

Any tips on what is the right way to go about doing this?

score 0 · Answer 1 · answered Jan 10 '17 at 06:44

V0(10) is an array of length 10, while c(1,1,1,-1,-1,-1) has length 6.

The warning that you are getting ("longer object length is not a multiple of shorter object length") is because 6 does not divide 10.

When you do v0(10) * c(1,1,1,-1,-1,-1), R repeats the second array as many times in order to create an array of the same length as v0(10). How? Like this:

v0(10) * c(1,1,1,-1,-1,-1,1,1,1,-1)

If this is not the result you wish to obtain, then either correct v0(10), the second array, or create a function where you define the correct operation between these two arrays.

Thanks for the help! I see what you mean! I am sorry if i was unclear in my question but it is exactly the function part that I am unable to do. Would really appreciate it if you could offer your help. — Eddie Wu, Jan 10 '17 at 07:16

score 0 · Answer 2 · edited May 23 '17 at 12:33

0

You can do something like,

v1 <- function(n){
  t <- seq(1:n)
  t[c(rep(FALSE, 3), rep(TRUE, 3))] <- t[c(rep(FALSE, 3), rep(TRUE, 3))] * (-1)
  return(t)
  }

v1(10)
# [1]   1   2   3  -4  -5  -6   7   8   9 -10

Also have a read at this for more info about the warning

edited May 23 '17 at 12:33

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answered Jan 10 '17 at 08:07

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Multiplying vectors of different length in R

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