R Program to Extract a Substring from a String

Introduction

Extracting a substring from a string is a common operation in text processing, often used to retrieve specific parts of a string based on position. In R, you can extract substrings using the substr() or substring() function. This guide will walk you through writing an R program that extracts a substring from a user-provided string based on specified start and end positions.

Problem Statement

Create an R program that:

• Prompts the user to enter a string.
• Prompts the user to specify the start and end positions for the substring.
• Extracts the substring based on the specified positions.
• Displays the extracted substring.

Example:

• Input:
  • Original string: "Hello, World!"
  • Start position: 8
  • End position: 12
• Output: Extracted substring: "World"

Solution Steps

1. Prompt the User for Input: Use the readline() function to take the original string, start position, and end position as input from the user.
2. Extract the Substring: Use the substr() function to extract the substring based on the specified start and end positions.
3. Display the Extracted Substring: Use the print() function to display the extracted substring.

R Program

# R Program to Extract a Substring from a String

# Step 1: Prompt the user to enter the original string
input_string <- readline(prompt = "Enter the original string: ")

# Step 2: Prompt the user to enter the start position for the substring
start_position <- as.numeric(readline(prompt = "Enter the start position: "))

# Step 3: Prompt the user to enter the end position for the substring
end_position <- as.numeric(readline(prompt = "Enter the end position: "))

# Step 4: Extract the substring
extracted_substring <- substr(input_string, start_position, end_position)

# Step 5: Display the extracted substring
print(paste("Extracted Substring:", extracted_substring))

Explanation

Step 1: Prompt the User to Enter the Original String

• The readline() function prompts the user to enter a string, storing the input in the variable input_string.

Step 2: Prompt the User to Enter the Start Position

• The readline() function prompts the user to enter the start position for the substring, which is then converted to a numeric value using as.numeric().

Step 3: Prompt the User to Enter the End Position

• The readline() function prompts the user to enter the end position for the substring, which is also converted to a numeric value using as.numeric().

Step 4: Extract the Substring

• The substr() function is used to extract the substring from input_string starting at start_position and ending at end_position.

Step 5: Display the Extracted Substring

• The print() function is used to display the extracted substring along with a descriptive message.

Output Example

Example:

Enter the original string: Hello, World!
Enter the start position: 8
Enter the end position: 12
[1] "Extracted Substring: World"

Example with Different Positions:

Enter the original string: R Programming
Enter the start position: 3
Enter the end position: 11
[1] "Extracted Substring: Programm"

Conclusion

This R program demonstrates how to extract a substring from a string using the substr() function. It covers essential operations such as taking user input, specifying start and end positions, extracting the substring, and displaying the result. Extracting substrings is a fundamental operation in text processing and is widely used in data manipulation tasks. This example is particularly useful for anyone learning R programming and string manipulation techniques.