ac3.R

log_factorial <- function (n) {
  # Return the log of factorial(n) for any integer n > 0
  if (n <= 1)
    return (0)
  return (log(n) + log_factorial(n - 1))
}

sum_log_factorial <- function (n) {
  # Return the sum of log_factorial(i) for i in 1..n
  sum <- 0
  for(i in seq(1, n, 1)) {
    sum <- sum + log_factorial(i)
  }
  return (sum)
}

fibonacci <- function(n) {
  # Return nth Fibonacci number
  if (n <= 1)
    return (n)
  return (fibonacci(n - 1) + fibonacci(n - 2))
}

time_f = function(f, n) system.time(f(n))[1]

options(expressions=500000)

time.complex <- function(ns, f) data.frame(seconds = sapply(ns, function(n) time_f(f, n)), Ns = ns)

ggp.time <- function(ns, f, lab) ggplot(time.complex(ns, f), aes(Ns)) + 
  geom_line(aes(y = seconds)) +
  ggtitle(paste(lab, "Times", " "))

ggp.time(c(50, 100, 200, 500, 1000, 2000, 3000), log_factorial, "Log Factorial")
ggp.time(c(50, 100, 200, 300, 500, 750, 1000, 1500, 2000, 2500, 3000), sum_log_factorial, "Sum Log Factorial")
ggp.time(c(5, 10, 15, 20, 25, 30, 35), fibonacci, "Fibonacci")