The “regexpr” Function in R

• Package: Base R (No specific package, it’s a built-in function)

• Purpose: To find the position of the first occurrence of a pattern in a character vector.

• General Class: String Manipulation

• Required Argument(s):

• pattern: A character string or a regular expression specifying the pattern to be searched.

• text: A character vector in which to search for the pattern.

• Notable Optional Arguments:

• ignore.case: Logical. If TRUE, the pattern matching is case-insensitive. The default is FALSE.

• perl: Logical. If TRUE, use Perl-style regular expressions. The default is FALSE.

• Example:

• # Example usage
  sentence <- "The quick brown fox jumps over the lazy dog."
  
  # Find the position of the first occurrence of "fox" (case-sensitive)
  pattern_position <- regexpr(pattern = "fox", text = sentence)
  
  print(pattern_position)

• In this example, regexpr is a built-in function in base R, and it is used to find the position of the first occurrence of the specified pattern (“fox”) in a character vector (sentence). The pattern and text arguments are required, and additional optional arguments, such as ignore.case and perl, can be used to modify the behavior of the pattern matching. The result is an integer vector indicating the starting position of the first occurrence of the pattern in each element of the input vector.