R Programming: Get all Prime numbers up to a given number

R Programming: Basic Exercise-6 with Solution

Write a R program to get all prime numbers up to a given number (based on the sieve of Eratosthenes).

Sample Solution :

R Programming Code :

# Define a function 'prime_numbers' that takes a single argument 'n'
prime_numbers <- function(n) {

  # Check if 'n' is greater than or equal to 2
  if (n >= 2) {
    
    # Create a sequence from 2 to 'n'
    x = seq(2, n)
    
    # Initialize an empty vector to store prime numbers
    prime_nums = c()
    
    # Loop through each number in the sequence from 2 to 'n'
    for (i in seq(2, n)) {
      
      # Check if 'i' is in the sequence 'x'
      if (any(x == i)) {
        
        # Add 'i' to the 'prime_nums' vector
        prime_nums = c(prime_nums, i)
        
        # Remove multiples of 'i' from the sequence 'x'
        x = c(x[(x %% i) != 0], i)
      }
    }
    
    # Return the vector of prime numbers
    return(prime_nums)
  }
  else {
    # Stop the function execution and display an error message if 'n' is less than 2
    stop("Input number should be at least 2.")
  }
} 

# Call the 'prime_numbers' function with an argument of 12
prime_numbers(12)

Output:

[1]  2  3  5  7 11                         

Explanation:

• Define Function: prime_numbers <- function(n) defines a function named prime_numbers that takes a single argument n.
• Check Input Validity: if (n >= 2) checks if n is at least 2. If not, it stops execution and returns an error message.
• Initialize Sequence: x = seq(2, n) creates a sequence of integers from 2 to n.
• Initialize Prime List: prime_nums = c() initializes an empty vector to store prime numbers.
• Loop Through Numbers: for (i in seq(2, n)) iterates over each number i from 2 to n.
• Check for Prime: if (any(x == i)) checks if i is still in the sequence x (i.e., it has not been marked as a non-prime).
• Add to Prime List: prime_nums = c(prime_nums, i) adds i to the prime_nums vector if it is prime.
• Mark Multiples as Non-Prime: x = c(x[(x %% i) != 0], i) removes all multiples of i from x and retains i.
• Return Result: return(prime_nums) returns the vector of prime numbers found.
• Function Call: prime_numbers(12) calls the function with n = 12 to get all prime numbers up to 12.

R Programming Code Editor:

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