HW 2: Review on Vectors, Tibbles, and Pipes

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Multiple Choice (10)

1) Which of these do not create a vector in R?

a) c(1, 5, 8, 9) b) c(1) c) 1:10 d) (1, 2, 3, 4, 5)

2) Identify the function being used in the following code snippet:

c(6, 3, 2)

a) () b) 6 c) c() d) []

3) What is the result of the following code?

c(6, 3, 2) + c(3, 2, 1)

a) c(9, 6, 3) b) c(9, 5, 3) c) c(18, 6, 2) d) An error

4) What does the following code return?

c("apple", "banana", "economics") %>% length()

a) "economics" b) 3 c) 9 d) A character vector

5) Which of the following creates a vector with exactly five elements?

a) 1:5 b) rep(1, 5) c) sample(1:10, size = 5, replace = FALSE) d) All of the above

6) Which statement about sample() is true?

a) It always returns the same output when run multiple times b) It can return duplicate values only if replace = TRUE c) It only works with numeric vectors d) It always returns a sorted vector

7) In a tibble, columns are best thought of as

a) Lists b) Matrices c) Vectors d) Functions

8) Which rule must be satisfied when creating a tibble?

a) Columns can have different lengths b) Columns must be named c) Rows must be named d) Columns must be numeric

9) Suppose us_data is a tibble. What does the following code return?

us_data %>% names()

a) The number of rows b) The number of columns c) A character vector of column names d) A tibble with one row

10) What does the pipe operator %>% do?

a) Combines vectors b) Inserts the left-hand object into the first argument of the next function c) Assigns variables d) Prints output to the console

Short Answer (5)

SA1) What does the function c() do in R? Answer in one sentence.

SA2) What is the difference between a numeric vector and a character vector? Give a short example of each.

SA3) In a tibble, what is the difference between a variable and an observation?

SA4) Rewrite the following code using a pipe:

names(us_data)

SA5) Why is piping often preferred over nested function calls like g(f(x))? Answer briefly in plain language.

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