Question 1
Suppose I define the following function in R
cube <- function(x, n) { x^3 } What is the result of running
cube(3) in R after defining this function?
Answer
The number 27 is returned
Explanation
Because 'n' is not evaluated, it is not needed even though it is a formal argument.
cube <- function(x, n) {
-
x^3 - }
cube(3) [1] 27 Question 2
The following code will produce a warning in R.
x <- 1:10 if(x > 5) { x <- 0 } Why?
Answer
'x' is a vector of length 10 and 'if' can only test a single logical statement.
Explanation
if(x > 5) {
-
x <- 0 - } Warning message: In if (x > 5) { : the condition has length > 1 and only the first element will be used Question 3
Consider the following function
f <- function(x) { g <- function(y) { y + z } z <- 4 x + g(x) } If I then run in R
z <- 10 f(3) What value is returned?
Answer
10
Explanation
f <- function(x) {
-
g <- function(y) { -
y + z -
} -
z <- 4 -
x + g(x) - }
z <- 10 f(3) [1] 10 Question 4
Consider the following expression:
x <- 5 y <- if(x < 3) { NA } else { 10 } What is the value of 'y' after evaluating this expression?
Answer
10
Explanation
x <- 5 y <- if(x < 3) {
-
NA - } else {
-
10 - }
y [1] 10 Question 5
Consider the following R function
h <- function(x, y = NULL, d = 3L) { z <- cbind(x, d) if(!is.null(y)) z <- z + y else z <- z + f g <- x + y / z if(d == 3L) return(g) g <- g + 10 g }