Which of the following function is used for searching text strings by means of regular expression?

The correct answer is D.

grepd, grepl, and gepexpr are all functions used for searching text strings by means of regular expression.

grepd is a function in the R programming language that searches for a regular expression pattern in a character vector. The pattern can be a simple string or a more complex regular expression. The function returns a logical vector indicating whether each element of the character vector matches the pattern.

grepl is a function in the R programming language that searches for a regular expression pattern in a character vector. The pattern can be a simple string or a more complex regular expression. The function returns a vector of integers indicating the positions of the matches in the character vector.

gepexpr is a function in the R programming language that searches for a regular expression pattern in a character vector. The pattern can be a simple string or a more complex regular expression. The function returns a list of objects, each of which contains information about a match. The list includes the position of the match, the length of the match, and the text of the match.

Here is an example of how to use grepd to search for a regular expression pattern in a character vector:

grepd("^[a-z]+$", "Hello World")

This will return a logical vector with a value of TRUE for each element of the character vector that matches the pattern, and a value of FALSE for each element that does not match the pattern. In this case, the vector will have a value of TRUE for the first element, because the first element of the character vector is “Hello”, which starts with a lowercase letter and ends with a lowercase letter. The vector will have a value of FALSE for the second element, because the second element of the character vector is “World”, which does not start with a lowercase letter and does not end with a lowercase letter.

Here is an example of how to use grepl to search for a regular expression pattern in a character vector:

grepl("^[a-z]+$", "Hello World")

This will return a vector of integers indicating the positions of the matches in the character vector. In this case, the vector will have a value of 1, because the first element of the character vector matches the pattern.

Here is an example of how to use gepexpr to search for a regular expression pattern in a character vector:

gepexpr("^[a-z]+$", "Hello World")

This will return a list of objects, each of which contains information about a match. The list includes the position of the match, the length of the match, and the text of the match. In this case, the list will have one element, which contains the information about the match at position 1. The information in the list will be as follows:

• match.position: 1
• match.length: 5
• match.text: “Hello”