Determine if there are x consecutive duplicates in a vector in R

Question

I have the following vector:

p<-c(0,0,1,1,1,3,2,3,2,2,2,2)

I'm trying to write a function that returns TRUE if there are x consecutive duplicates in the vector.

The function call found_duplications(p,3) will return True because there are three consecutive 1's. The function call found_duplications(p,5) will return False because there are no 5 consecutive duplicates of a number. The function call found_duplications(p,4) will return True because there are four consecutive 4's.

I have a couple ideas. There's the duplicated() function:

duplicated(p)
> [1] FALSE  TRUE FALSE  TRUE  TRUE FALSE FALSE  TRUE  TRUE  TRUE  TRUE  TRUE

I can make a for loop that counts the number of TRUE's in the vector but the problem is that the consecutive counter would be off by one. Can you guys think of any other solutions?

Answer 1

You could also do

find.dup <- function(x, n){
 n %in% rle(x)$lengths
}

find.dup(p,3)
#[1] TRUE
find.dup(p,2)
#[1] TRUE
find.dup(p,5)
#[1] FALSE
find.dup(p,4)
#[1] TRUE

Answer 2

p<-c(0,0,1,1,1,3,2,3,2,2,2,2)

find.dup <- function(x, n) {
  consec <- 1
  for(i in 2:length(x)) {
    if(x[i] == x[i-1]) {
      consec <- consec + 1
    } else {
      consec <- 1
    }
    if(consec == n)
      return(TRUE) # or you could return x[i]
  }
  return(FALSE)
}

find.dup(p,3)
# [1] TRUE

find.dup(p,4)
# [1] TRUE

find.dup(p,5)
# [1] FALSE