R Programming Questions and Answers – Control Structures – 1

This set of R Programming Language Multiple Choice Questions & Answers (MCQs) focuses on “Control Structures – 1”.

1. Which of the following is valid syntax for if else statement in R?
a)

if(<condition>) {
          ## do something
}
else {
          ## do something else
}

b)

if(<condition>) {
          ## do something
}
elseif {
          ## do something else
}

c)

if(<condition>) {
          ## do something
}
else if {
          ## do something else
}

d)

if(<condition>) {
          ##& do something
}
else {
          ##@ do something else
}

2. Point out the correct statement?
a) Blocks are evaluated until a new line is entered after the closing brace
b) Single statements are evaluated when a new line is typed at the start of the syntactically complete statement
c) The if/else statement conditionally evaluates two statements
d) Break will execute a loop while a condition is true
View Answer

3. Which of the following R syntax is correct for while loop?
a) while ( statement1 ) statement2
b) while ( statement1 ) else statement2
c) while ( statement1 ) do statement2
d) while ( statement2 ) doelse statement2
View Answer

4. Which of the following R code generate a uniform random number?
a)

x <- runif(1, 0, 10)
if(x > 3) {
    y <- 10
} else {
    y <- 0
}

b)

x <- run(1, 0, 10)
if(x > 3) {
    y <- 10
} else {
    y <- 0
}

c)

x <- random(1, 0, 10)
if(x > 3) {
    y <- 10
} else {
    y <- 0
}

d)

x <- random(1, 0, 10)
if(x > 1) {
    y <- 0
} else {
    x <- 0
}

5. Point out the wrong statement?
a) for will execute a loop a fixed number of times
b) break will execute a loop while a condition is true
c) if and else tests a condition and acting on it
d) break is used to break the execution of a loop
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6. _______ is used to break the execution of a loop.
a) next
b) skip
c) break
d) delete
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7. Which of the following R code generate a sequence of integers from 1 to 10?
a)

> for(i in 1:9) {
    + print(i)
+ }
[1]

b)

> for(i in 0:9) {
    + print(i)
+ }
[1]

c)

> for(i in 1:10) {
    + print(i)
+ }
[1]

d)

> for(i in 2:50) {
    + print("i")
+ }
[1]

8. Which of the following statement can be used to explicitly control looping?
a) if
b) while
c) break
d) for
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9. Which of the following should be preferred for evaluation from list of alternatives?
a) subsett
b) eval
c) switch
d) set
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10. What will be the output of the following R code?

> x <- c("a", "b", "c", "d")
> for(i in 1:4) {
    + ## Print out each element of 'x'
    + print(x[i])
+ }

a)

[1] "a"
[1] "b"
[1] "c"
[1] "d"

b)

[1] "c"
[1] "b"
[1] "a"
[1] "d"

c)

[1] "d"
[1] "c"
[1] "b"
[1] "a"

d) Error
View Answer

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