Skip to content

Week 2 Quiz:R Programming(Data Science Specialization):Answers2025

Question 1

Suppose I define the following function:

cube <- function(x, n) {
x^3
}
cube(3)

✅ The number 27 is returned
❌ An error is returned because ‘n’ is not specified
❌ The user is prompted to specify ‘n’
❌ A warning is given

Explanation:
The function ignores n. It simply computes x^3, so cube(3) → 3³ = 27.

Question 2

x <- 1:10
if(x > 5) {
x <- 0
}

✅ ‘x’ is a vector of length 10 and ‘if’ can only test a single logical statement.
❌ Syntax incorrect
❌ No elements greater than 5
❌ Can’t assign scalar to vector

Explanation:
if() expects a single TRUE/FALSE value, not a logical vector. Hence R issues a warning.

Question 3

f <- function(x) {
g <- function(y) {
y + z
}
z <- 4
x + g(x)
}
z <- 10
f(3)

✅ 10
❌ 7
❌ 16
❌ 4

Explanation:
Inside f, z = 4 (local variable).
g(x) = 3 + 4 = 7; then x + g(x) = 3 + 7 = 10.
Outer z=10 is ignored due to lexical scoping.

Question 4

x <- 5
y <- if(x < 3) {
NA
} else {
10
}

✅ 10
❌ 5
❌ 3
❌ NA

Explanation:
x < 3 is FALSE, so the else block runs — y = 10.

Question 5

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
}

✅ f
❌ z
❌ d
❌ g
❌ L

Explanation:
f is referenced but never defined inside or passed as argument — hence it’s a free variable.

Question 6

✅ A collection of symbol/value pairs
❌ A list of functions
❌ A special type of function
❌ An R package

Explanation:
An environment is a collection (like a map) of variable names (symbols) bound to values.

Question 7

✅ Lexical scoping
❌ Global
❌ Dynamic
❌ Compilation

Explanation:
R uses lexical (static) scoping — free variables are resolved from where the function was defined, not called.

Question 8

✅ The values of free variables are searched for in the environment in which the function was defined.
❌ Environment where called
❌ Working directory
❌ Global environment

Explanation:
Lexical scoping means lookup happens in the defining environment, not the calling one.

Question 9

✅ All objects must be stored in memory
❌ Cannot be >100 MB
❌ Functions cannot be nested
❌ All objects can be stored on disk

Explanation:
R primarily keeps objects in-memory while running (exceptions use external memory techniques).

Question 10

✅ It is the environment in which a function was called.
❌ Always global
❌ Package search list
❌ Environment where defined

Explanation:
The parent frame refers to the calling environment, not the defining environment.

🧾 Summary Table

Q# ✅ Correct Answer Key Concept
1 The number 27 Function ignores unused arg
2 if only tests single logical Vector vs scalar logic
3 10 Lexical scoping, local variable
4 10 if-else evaluation
5 f Free variable concept
6 Symbol/value pairs Environment structure
7 Lexical scoping Variable resolution rule
8 Searched where defined Function environment
9 Stored in memory Memory model of R
10 Called environment Parent frame meaning