R Programming Basics Quiz

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Questions and Answers

What does the round() function do when applied to a vector?

Multiplies each element by 2
Rounds each element individually to the nearest integer (correct)
Returns the largest element in the vector
Calculates the average of the elements

In R, scalars are treated as single-element vectors.

True (A)

What is the result of applying the function round() to the number 1.2?

The function f(x, c) returns the value of (x + c) ________.

squared Signup and view all the answers

Match the R function with its description:

round() = Rounds to the nearest integer sqrt() = Calculates the square root f(x,c) = Returns (x+c)^2 recycling = Extending a shorter vector to match a longer one Signup and view all the answers

What happens when you try to call the function f() with a vector as the second argument?

It results in an error (B) Signup and view all the answers

The + operator in R is treated as a function.

True (A) Signup and view all the answers

What is the expected output of the function f(1:3, 1)?

4 9 16 Signup and view all the answers

What is the main purpose of the subset() function in R?

To handle NA values automatically (C) Signup and view all the answers

The which() function in R returns the values that satisfy a given condition.

False (B) Signup and view all the answers

What does the filtering expression `x[x > 5]` return if `x` contains NA values?

It returns the values greater than 5, including NA where applicable. Signup and view all the answers

The function used to identify the positions within a vector where a condition holds is called _____ function.

which Signup and view all the answers

Match the R operation with its output:

z[c(TRUE,FALSE,TRUE,TRUE)] = Extracts elements based on TRUE/FALSE x[x > 5] = Returns values greater than 5 with NA included subset(x, x > 5) = Returns values greater than 5 without NA which(z*z > 8) = Returns indices of values that satisfy the condition Signup and view all the answers

What does the code `first1 <- x[ifelse(x > 6, 2x, 3x)]` evaluate?

It creates a vector with elements multiplied conditionally (B) Signup and view all the answers

The result of the expression `z * z > 8` is a vector of Boolean values.

True (A) Signup and view all the answers

What is the advantage of using ifelse() over traditional if-then-else constructs in R?

It is vectorized and potentially much faster. Signup and view all the answers

What does the expression `x[j,]` return?

Rows of x specified by the true elements of j (C) Signup and view all the answers

The operation of filtering rows using a Boolean vector is not vectorized.

False (B) Signup and view all the answers

What operator is used for calculating the logical AND of two Boolean vectors in R?

& Signup and view all the answers

The command `z <- x[z %% 2 == 1,]` extracts rows of x where the elements of z are ___ numbers.

odd Signup and view all the answers

What does the function `drop` do when applied in data operations?

It retains the two-dimensional nature of data. (D) Signup and view all the answers

Using `&&` will yield the same result as using `&` for logical operations on vector elements.

False (B) Signup and view all the answers

If we apply the expression `m[m[,1] > 1 & m[,2] > 5,]`, what type of rows are extracted from m?

Rows where the first column is greater than 1 and the second column is greater than 5. Signup and view all the answers

Match the following commands with their functionalities:

j <- x[,2] >= 3 = Identifies which elements in column 2 are at least equal to 3 z <- x[z %% 2 == 1,] = Extracts rows with odd values in z m[m[,1] > 1 & m[,2] > 5,] = Extracts rows based on multiple conditions drop = TRUE = Retains the two-dimensional structure of data Signup and view all the answers

What function is used to add columns to a matrix in R?

cbind() (A) Signup and view all the answers

The rbind() function can be used to add rows to an existing matrix.

True (A) Signup and view all the answers

What happens to the original matrix when you reassign a new matrix to it?

The original matrix is replaced and no longer exists. Signup and view all the answers

Using the `cbind()` function allows you to bind a column of ______ to the existing matrix.

values Signup and view all the answers

When creating a matrix in a loop, it is more efficient to:

Allocate a large matrix first. (C) Signup and view all the answers

Match the function to its description:

rbind() = Combines rows of matrices cbind() = Combines columns of matrices matrix() = Creates a new matrix dim() = Returns the dimensions of a matrix Signup and view all the answers

What is the time penalty mentioned when repeatedly creating a matrix?

Time taken to allocate memory each time a new matrix is created. Signup and view all the answers

In R, using the function `______()` allows for the recycling of values when creating a new matrix.

cbind Signup and view all the answers

What type of data structure is suggested for storing employee information?

List (B) Signup and view all the answers

The numerical indices of list components must always be used when accessing data in a list.

False (B) Signup and view all the answers

What Boolean value indicates that an employee is a member of a union?

TRUE Signup and view all the answers

To access a specific component of a list by name, you can use the syntax `j$______`.

salary Signup and view all the answers

Which of the following methods can be used to access the salary component of a list named j?

All of the above (D) Signup and view all the answers

Match the following methods of accessing list components with their descriptions:

lst$c = Accessing component by name using dollar sign lst[["c"]] = Accessing component by name using double brackets lst[[i]] = Accessing component by numerical index lst["c"] = Accessing component by name returning a sublist Signup and view all the answers

Using single brackets to access a list component returns an element in the original data type.

False (B) Signup and view all the answers

What is the advantage of using names instead of numerical indices in lists?

Clarity and less chance of error Signup and view all the answers

What type of vector is the result of using unlist() on the list containing the values "Joe", "55000", and "TRUE"?

Character vector (D) Signup and view all the answers

The unlist() function will always return a numeric vector if the original list contains numeric values.

False (B) Signup and view all the answers

What function is used to concatenate lists in R, which also includes an option for recursive flattening?

c() Signup and view all the answers

In R, when using the function unlist(), the components of the list are coerced to a common mode, typically resulting in a ____________ vector.

character Signup and view all the answers

Match the following terms with their descriptions:

unlist() = Converts a list to a vector c() = Concatenates objects length() = Returns the number of components recursive = Option for flattening lists during concatenation Signup and view all the answers

What is the result of calling the c() function with the recursive argument set to TRUE on a list where the components themselves are lists?

A single flattened list (C) Signup and view all the answers

When combining lists, the default value for the recursive argument in the c() function is TRUE.

False (B) Signup and view all the answers

What type does R choose when mixing numeric and character types in a list during unlist()?

character Signup and view all the answers

Flashcards

Vectorized functions

Functions that operate on each element of a vector individually, rather than on the entire vector at once.

Recycling in R

R automatically extends shorter vectors to match the length of longer vectors when operating on them, leading to element-wise operations.