R/find_prime.R

In UBC-MDS/mlist_R: mlist

find_prime <- function(x){

  #' Usage: Find largest prime numbers within a vector of integers.
  #'
  #' @param x : a vector of integer less than 1000.
  #' @return an integer
  #'
  #' @export
  #' @examples
  #' find_prime(c(0,1,2,3,4,5))
  #' # returns 5
  #'
  #' find_prime(c(0,1))
  #' # returns "No prime number in vector"
  #'

  prime <- c(2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,101,103,107,109,113,127,131,137,139,149,151,157,163,167,173,179,181,191,193,197,199,211,223,227,229,233,239,241,251,257,263,269,271,277,281,283,293,307,311,313,317,331,337,347,349,353,359,367,373,379,383,389,397,401,409,419,421,431,433,439,443,449,457,461,463,467,479,487,491,499,503,509,521,523,541,547,557,563,569,571,577,587,593,599,601,607,613,617,619,631,641,643,647,653,659,661,673,677,683,691,701,709,719,727,733,739,743,751,757,761,769,773,787,797,809,811,821,823,827,829,839,853,857,859,863,877,881,883,887,907,911,919,929,937,941,947,953,967,971,977,983,991,997)

  #check if vector contains at least one element
  if (length(x) == 0) {

    stop("Input vector must have a length greater than zero.")
  }

  # check input type is vector

  if (!typeof(x) == "double"){
    stop("Input type must be a vector of numeric value")
  }


  #check if vector contains values less than 1000
  if (max(x)>1000){
    stop("Input values exceed 1000. Please limit range of input values to less than 1000.")
  }


  #return list of prime numbers
  list_prime <- round(intersect(prime, x))

  #return the largest prime numbers
  if (length(list_prime)>=1){
    return(max(list_prime))
  } else {

    return(print("No prime number in vector"))
  }

}