Chapter 2 Multiple choice questions

. What is the appropriate way to request the 10^th entry of the variable numberlist in R?

numberlist(10)

numberlist[10]

numberlist{10}

numberlist<10>

. The matrix K contains 8 row and 5 columns. How would you request the data from the 3^rd column?

K[ , 3]

K[3, ]

K[3]

K[8, 3]

. Which of the following lines of code will create a loop that repeats 15 times?

for (n in 15:30){}

n <- 5; while (n < 15){n <- n + 1}

for (n in 0:15){}

for (n in 83:97){}

. Which line of code correctly merges the two strings 'hap' and 'py' into a single string ('happy')?

c('hap','py')

paste('hap','py',sep='')

data.frame('hap','py')

paste('hap','py')

. The median function calculates the median of a vector of numbers. Which of the following lines of code returns a median of 7?

median(c(1,3,5,7,9))

median(c(1,3,5,7,11))

median(c(3,5,7,11,13))

median(c(1,3,5,7,7,9))

. If the data object 'a' contains the values 2, 4 and 6, what will be returned by the following line of code: a^3

5, 7, 9

6, 12, 18

8, 64, 216

9, 81, 729

. To tell an if statement to execute some code when the value of a is greater than or equal to 10, which expression would you use?

if (a > 10)

if (a < 10)

if (a <= 10)

if (a >= 10)

. Which of the following expressions is FALSE?

is.na(1/0)

is.infinite(1/0)

10>5

is.na(sqrt(-1))

. Which option is the correct R syntax for an if statement that prints the value of n when it is greater than 10?

if (n > 10)(print(n))

if (n > 10){print(n)}

if {n > 10}(print(n))

if {n > 10}{print(n)}

. The following code defines a function. What does it do?
mysteryfunction <- function(input1, input2){
numerator <- (input1 – input2)
denominator <- (input1 + input2)
output <- numerator/denominator
return(output)}

Calculates the difference between the inputs

Calculates the ratio of the two inputs

Divides the sum of the inputs by their difference

Divides the difference in inputs by their sum

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