Why is my recursive function so slow in R?

Question

The following takes about 30 seconds to run whereas I would expect it to be nearly instant. Is there a problem with my code?

x <- fibonacci(35);

fibonac         


        

Answer 1

If you are truly looking to return Fibonacci numbers and aren't using this example to explore how recursion works then you can solve it non-recursively by using the following:

fib = function(n) {round((1.61803398875^n+0.61803398875^n)/sqrt(5))}