Questions and answers for exam Preparation

MCQs

Total Questions : 10

Question 1. Point out the correct statement :

Empty vectors can be created with the vector() function
A sequence is represented as a vector but can contain objects of different classes
raw" objects are commonly used directly in data analysis
None of the mentioned

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Answer: Option A. -> Empty vectors can be created with the vector() function

A vector can only contain objects of the same class

Question 2. Which of the following statement changes column name to h and f ?

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Answer: Option A. -> colnames(m)

Column names and row names can be set separately using the colnames() and rownames() functions.

Question 3. Point out the wrong statement :

matrices or more generally arrays are multi-dimensional generalizations of vectors
factors provide compact ways to handle categorical data
vectors provide a convenient way to return the results of a statistical computation
All of the mentioned

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Answer: Option C. -> vectors provide a convenient way to return the results of a statistical computation

The dimension attribute is itself an integer vector of length 2 (number of rows, number of columns).

Question 4. Data frames can be converted to a matrix by calling data._______

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Answer: Option C. -> matrix()

as.matrix() function should be used to coerce a data frame to a matrix.

Question 5. Point out the correct statement :

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Answer: Option B. -> Number Inf represents infinity in R

This allows us to represent entities like 1 / 0.

Question 6. What would be the output of the following code ?x - vector("list", length = 5)x

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Answer: Option A. -> NULL

We can also create an empty list of a pre-specified length with the vector() function.

Question 7. What would be the output of the following code ?m - matrix(nrow = 2, ncol = 3)dim(m)

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Answer: Option B. -> 2 3

Matrices are constructed column-wise.

Question 8. Point out the correct statement :

The usual operator, -, can be thought of as a syntactic short-cut to expression operation
Assignment can also be made using the function assignment()
Vectors can be used in arithmetic expressions, in which case the operations are performed element by element
None of the mentioned

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Answer: Option C. -> Vectors can be used in arithmetic expressions, in which case the operations are performed element by element

Vectors occurring in the same expression need not all be of the same length.

Question 9. What would be the output of the following code ?sqrt(-17)