Practice Library
All MCQs
Browse exam-wise, subject-wise, and country-wise MCQs with explanations.
Choose an option to check your answer.
A.
A container that can hold elements of different types and structures
B.
A vector restricted to logical values
C.
A matrix with one column
D.
A function that sorts rows
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Correct Answer: A. A container that can hold elements of different types and structures
Explanation:
Lists can contain vectors, data frames, functions, or even other lists.
Choose an option to check your answer.
A.
rbind()
B.
append_rows()
C.
factor()
D.
cbind()
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Correct Answer: D. cbind()
Explanation:
cbind() binds objects by column and therefore adds variables horizontally.
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A.
cbind()
B.
merge_levels()
C.
rbind()
D.
unlist()
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Correct Answer: C. rbind()
Explanation:
rbind() binds objects by row and therefore adds observations vertically.
Choose an option to check your answer.
A.
To remove duplicate rows
B.
To repeat values according to a specified pattern
C.
To fit a regression model
D.
To rename a package
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Correct Answer: B. To repeat values according to a specified pattern
Explanation:
rep() creates repeated sequences or repeated individual elements.
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A.
seq()
B.
sum()
C.
replicate_plot()
D.
levels()
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Correct Answer: A. seq()
Explanation:
seq() can specify the starting value, ending value, step size, or desired length.
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A.
Five random numbers
B.
A vector containing only 1 and 5
C.
A five-level factor
D.
The integer sequence 1, 2, 3, 4, 5
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Correct Answer: D. The integer sequence 1, 2, 3, 4, 5
Explanation:
The colon operator creates a regular sequence with a step of one.
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A.
Converting all data to graphics
B.
Saving a vector as an image
C.
Applying an operation to an entire vector without an explicit element-by-element loop
D.
Sorting only character values
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Correct Answer: C. Applying an operation to an entire vector without an explicit element-by-element loop
Explanation:
Many R operations automatically work across every element of a vector.
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A.
df[age <- 30]
B.
df[df$age > 30, ]
C.
df$age[30, ]
D.
df(30 > age)
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Correct Answer: B. df[df$age > 30, ]
Explanation:
The logical condition identifies qualifying rows, and the blank column position keeps all columns.
Choose an option to check your answer.
A.
The number of rows in df
B.
The number of columns in df
C.
The number of missing cells only
D.
The row names as text
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Correct Answer: A. The number of rows in df
Explanation:
nrow() reports the number of observations in a rectangular object.
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A.
tailor()
B.
first()
C.
rows()
D.
head()
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Correct Answer: D. head()
Explanation:
head() provides a quick view of the beginning of an object.
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A.
Equal numeric spacing
B.
No labels
C.
A meaningful ranking
D.
Only two possible values
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Correct Answer: C. A meaningful ranking
Explanation:
Ordered factors represent categories such as low, medium, and high.
Choose an option to check your answer.
A.
Unstructured image pixels
B.
Categorical data with defined levels
C.
A random-number generator
D.
Only continuous measurements
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Correct Answer: B. Categorical data with defined levels
Explanation:
Factors store categorical values together with their possible levels.
