Fibonacci Sequence Using Recursion in R

The first two terms of the Fibonacci sequence is 0 followed by 1. All other terms are obtained by adding the preceding two terms.

This means to say the n^th term is the sum of (n-1)^th and (n-2)^th term.

The Fibonacci sequence: 0, 1, 1, 2, 3, 5, 8, 13, 21

Example: Fibonacci Sequence in R

# Program to diplay the Fibonacci
# sequence up to n-th term using
# recursive functions

recurse_fibonacci <- function(n) {
    if(n <= 1) {
        return(n)
    } else {
        return(recurse_fibonacci(n-1) + recurse_fibonacci(n-2))
    }
}

# take input from the user
nterms = as.integer(readline(prompt="How many terms? "))

# check if the number of terms is valid
if(nterms <= 0) {
    print("Plese enter a positive integer")
} else {
    print("Fibonacci sequence:")
    for(i in 0:(nterms-1)) {
        print(recurse_fibonacci(i))
    }
}

Output

How many terms? 9
[1] "Fibonacci sequence:"
[1] 0
[1] 1
[1] 1
[1] 2
[1] 3
[1] 5
[1] 8
[1] 13
[1] 21

Here, we ask the user for the number of terms in the sequence.

A recursive function recurse_fibonacci() is used to calculate the nth term of the sequence. We use a for loop to iterate and calculate each term recursively.

See this page to find out how you can print fibonacci series in R without using recursion.