The document presents four different functions (fb1, fb2, fb3, fbcpp) for solving the FizzBuzz problem and benchmarks their performance on different sized test cases. fb3 is the fastest approach, using modulo operations and ifelse statements to vectorize the logic. The document then explores compiling fb1-fb3 to C++ using Rcpp to further improve performance, with fbcpp showing the fastest results.

26. > fizzbuzz <- function(n) {
# Write your code here
}
> fizzbuzz(20)
[1] "1" "2" "Fizz"
[4] "4" "Buzz" "Fizz"
[7] "7" "8" "Fizz"
[10] "Buzz" "11" "Fizz"
[13] "13" "14" "FizzBuzz"
[16] "16" "17" "Fizz"
[19] "19" "Buzz"

28. fb1 <- function(n) {
fb <- character(n)
for (i in 1:n) {
if (i %% 3 == 0 && i %% 5 == 0)
fb[i] <- "FizzBuzz"
else if (i %% 3 == 0)
fb[i] <- "Fizz"
else if (i %% 5 == 0)
fb[i] <- "Buzz"
else
fb[i] <- i
}
fb
}

30. fb2 <- function(n) {
sapply(1:n, function(i) {
if (i %% 3 == 0 && i %% 5 == 0)
"FizzBuzz"
else if (i %% 3 == 0)
"Fizz"
else if (i %% 5 == 0)
"Buzz"
else
i
})
}

35. fb3 <- function(n) {
isFizz <- rep(c(F,F,T), length=n)
isBuzz <- rep(c(F,F,F,F,T), length=n)
isNumber <- !isFizz & !isBuzz
fizz <- ifelse(isFizz, "Fizz", "")
buzz <- ifelse(isBuzz, "Buzz", "")
number <- ifelse(isNumber, 1:n, "")
paste(fizz, buzz, number, sep="")
}

40. > N <- 100
> benchmark(fb1(N), fb2(N), fb3(N),
order="relative",
replications=10000)
test elapsed relative
3 fb3(N) 4.172 1.000000
2 fb2(N) 6.669 1.598514
1 fb1(N) 7.779 1.864573

41. > N <- 10000
> benchmark(fb1(N), fb2(N), fb3(N),
order="relative",
replications=100)
test elapsed relative
3 fb3(N) 2.907 1.000000
2 fb2(N) 7.823 2.691090
1 fb1(N) 8.200 2.820777

42. > N <- 1000000
> benchmark(fb1(N), fb2(N), fb3(N),
order="relative",
replications=5)
test elapsed relative
3 fb3(N) 28.287 1.000000
1 fb1(N) 46.198 1.633188
2 fb2(N) 52.223 1.846184

47. library(compiler) # Installed by default
library(inline) # Needs manual installation
fbcpp <- cxxfunction(
signature(ns="integer"),
body=src, # Shown in the next slide
plugin="Rcpp")
fb1.c <- cmpfun(fb1)
fb2.c <- cmpfun(fb2)
fb3.c <- cmpfun(fb3)
fbcpp.c <- cmpfun(fbcpp)

48. int n = Rcpp::as<int>(ns);
Rcpp::CharacterVector fb(n);
for (int index = 0; index < n; index++) {
int i = index + 1;
if (i % 3 == 0 && i % 5 == 0)
fb[index] = "FizzBuzz";
else if (i % 3 == 0)
fb[index] = "Fizz";
else if (i % 5 == 0)
fb[index] = "Buzz";
else {
char s[11]; // Integer is 10 or less digit
sprintf(s, "%d", i);
fb[index] = s;
}
}
return(fb);