Add to DIRECTORY.md

Author: ITZ-NIHALPATEL

DIRECTORY.md

@@ -85,6 +85,7 @@
   * [Fibonacci](https://github.com/TheAlgorithms/R/blob/HEAD/mathematics/fibonacci.r)
   * [First N Fibonacci](https://github.com/TheAlgorithms/R/blob/HEAD/mathematics/first_n_fibonacci.r)
   * [Greatest Common Divisor](https://github.com/TheAlgorithms/R/blob/HEAD/mathematics/greatest_common_divisor.r)
+  * [Palindrome Check](https://github.com/TheAlgorithms/R/blob/HEAD/mathematics/isPalindrome.r)
   * [Josephus Problem](https://github.com/TheAlgorithms/R/blob/HEAD/mathematics/josephus_problem.r)
   * [Least Common Multiple](https://github.com/TheAlgorithms/R/blob/HEAD/mathematics/least_common_multiple.r)
   * [Modular Exponentiation](https://github.com/TheAlgorithms/R/blob/HEAD/mathematics/modular_exponentiation.r)

mathematics/isPalindrome.r

@@ -1,4 +1,13 @@
-# Palindrome Number Checking in R
+#' Check if a number is a palindrome
+#'
+#' @description Checks if an integer is a palindrome (reads the same forwards
+#'   and backward) without using strings. Negative numbers are not palindromes.
+#' @param number The integer to check.
+#' @return TRUE if the number is a palindrome, FALSE otherwise.
+#' @examples
+#' isPalindrome(121)
+#' isPalindrome(123)
+
 isPalindrome <- function(number) {
   # Negative numbers are not considered palindromes
   if (number < 0L) {